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www.americanradiohistory.com Radio News for April, 1928 1089

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jrOINING the Radio Association enables you to cash Doubled Income in Six Months in on Radio now! Follow its success -proven plans "I attribute my success entirely to the Radio Associa- and you can earn $3 an hour, in your spare time, tion," writes W. E. Thon, Chicago, who was clerk-in a from the very first. Over $600,000,000 is being spent hardware store before joining. We helped him 4cure yearly for sets, supplies, service. You the managership of a large std re at can get your share of this business a 220% increased salary. and,tt the same time, fit yourself for the big -pay opportunities in Radio. What a Membership Can "In 1922 I was a clerk," writes K. O. Do for You Benzing, McGregor, Ia., "when I enrolled. Founded on a New Idea Since then I have built hundreds of sets- I- Enable you to earn $3 an hour from 1 -tube Regenerative to Supefhetero- Members of the Association do not upwards in your spare time. d ynes. I am now operating my o .i store wait for months before they make and my income is 200% greater thin when 2 -Train you to install, repair and I joined the Association. My entire success money out of Radio. Without quit- build all kinds of sets. is due to the splendid help it gave." ting their jobs. our members are 3 -Start you in business without earnin5 $25 to $75 a week spare time capital, or finance an invention. Easiest Way Into Radio by building "tailored" radio sets, 1 -Train you for the $3,000 to If ambitious to become a Radio;Engineer, serving as "radio doctors," selling $10,000 big -pay radio positions. to fit yourself for the $3,000 #o $10,000 ready built sets and accessories, or opportunities in Radio, the 5 -Help secure a join ssociation. better position It a following one of the many profit - at bigger pay for you. gives you comprehensive, practical and making plans of the Association. theoretical training and the be fit of our 6 -Give you the backing of the Employment Service. You ear while you Radio Association. Earned $500 in Spare Hours learn. You have the privileg of buying A MEMBERSHIP NEED NOT radio supplies at wholesale. u have the Association behind you in carrying out your Hundreds earn $3 an hour as "radio COST YOU A SINGLE CENT doctors." Lyle Follick, Lansing, ambitions. Mich., has already made $500 in spare ACT NOW you wish Special time. Werner Eichler, Rochester, -if N. Y., is earning $50 a week for spare time. F. J. Membership Ilan Buckley, Sedalia, Mo., is earning as much in spare To a limited number of ambitious men, we will give Special time as he receives from his employer. Memberships that may not -need not -cost you a cent. To secure one, write today. We will send you details and also We will start you in business. Our cooperative plan our book, "Your Opportunity in the Radio Industry." It will -given the ambitious man his opportunity to establish open your eyes to the money -making possibilities of Radio. himself. Many have followed this plan and es- Write today. tablished radio stores. Membership in the Association has increased the salaries of many. Scores are now r connected with big radio organizations. Others have RADIO ASSOCIATION OF AMERICA, prosperous stores. 4513 Ravenswood Ave., Chicago, III. Dept. RN -4 A year ago Claude De Grave knew nothing about Radio. Gentlemen: Today he is on the staff of a famous radio manufac- Please send me by return mail full details of your Special Membership Plan and also copy of your book, "Your Oppor- turer and an associate member of the Institute of Radio tunity in the Radio Industry." Engineers. He attributes his success to joining the As- sociation. His income now is 350% more than when Name he joined. Address City State

www.americanradiohistory.com 1090 Radio News for April, 1928 \ \ \ i/

Published by EXPERIMENTER PUBLISHING COMPANY, Inc., Publishers of "Radio News," "Science and Invention,' "Radio Listeners' Guide," "Amazing Stories" and "French Humor." H. GERNSBACK, President S. GERNSBACK, Treasurer C. E. ROSENFELT, Secretary Member: Audit Bureau of Circulations Radio Magazine Publishers Association Editorial and General Offices . . 230 Fifth Avenue, New York City VOLUME 9 APRIL, 1928 NUMBER 10

Contents of This Issue: Radio News' New Policy .1 Novel Alitonlatie Volume Control By Hugo Gernsback 1097 By Harold A. Wheeler 1181 Television Comes to the Home, A Really Portable Radio Set, By G. C. B. Rowe 1098 By J. B. Armstrong 1132 Home Radio Photography 1101 What Constitutes Tone Quality (Part II), The Listener Speaks 1104 By Robert Neil Auble 1134 Favorite Broadcast Artists 1105 Controlling Volume in Your Receiver, When the "SOS" Flashes! By John B. Brennan, Jr. 1136 By Orrin E. Dunlap 1108 How Powerful a Tube Does Your Set The Old Dray Mare, Need 1137 By Robert Francis Smith 1110 The Action of "B" Socket -Power Units, Broadcastatics 1112 By Herndon Green 1138 Dr. de Forest Talks on Real" 1113 How to fick an Audio Amplifier, By Fred H, Canfield 1140 The Newest in Radio Equipment 1114 Radio in Every Hotel Room 1115 Transmitting on a Wavelength of Three The Radio School Teacher is Here, Quarters of a Meter, By Armstrong Perry 1116 By H. E. Hohmann, 1143 What's New in Radio 1118 Letters from Home Radio Set 000 Monthly Prize for Set Builders 1119 Constructors 1146 'When Radio Turns Street Lamplighter RADIO NEWS LABORATORIES 1148 By S. R. Winters 1120 Iladiotics 1150 List of Broadcast Stations 1121 I Want to Know, - By C. W. Palmer 1151 "Weighing In" Radio Stations, Why Batteries are Still in Fashion for By A Binneweg, Jr. 1122 Short -Wave Receivers 1158 Whispering Across the Hudson River, Some Suggestions About Resistance By Joseph Riley 1123 Coupling 1170 The Radio Beginner -What a Radio Tube Radio "Bugs" 1172 is and What it Does, Short -Wave Broadcast Information, By Clyde A. Randon 1124 By E. T. Somerset 1174 An IL-I?. Short -Wave Broadcast Receiver Short -Wave Data Wanted 1175 ($100 Prize Winner) What the Federal Radio Commission By W. Francis Goodrean 1126 Needs 118i

In Forthcoming issues: THE "R.F. BOOSTER UNIT" COMING-A PROGRAM POOL? HOW BROADCASTING IS ACCOMPLISHED By David Grimes By Charles Magee Adams By G. C. B. Rowe Titis well -known radio engineer has designed There remains now hardly an unsolved prob- The workings of the radio receiver are well a novel instrument for use with any radio lem in the technique of radio broadcasting known to most readers, and the broadcast receiver to increase range and selectivity. It except this little one -fete shall bear the studio shows little that is mysterious. This crut he plugged in or out as receiving con- expense? Mr. Adams' comments will inter- article explains in simple language the ditions vary. est every listener. laborious processes that lie between. RADIO NEWS is published on the 10th of each preceding month. There are 12 RADIO NI':Ws is for sale at all newsstands in the United States is $2.50 a year in U. S. and possessions. and Canada, numbers per year. Subs.-rinllon price and at ltrentann's, Arc. de LOpen. l'arts, France. European agents: S. J. Canada and foreign countries, $3.00 per year. U. S. Coin as well as U. S. Stamps Et Cie. 40 Place Verte, Antwerp. Belgium. Wise accepted Uno foreign coins or stumps). Single copies, 25 cents each. Checks and HOW TO SUBSCRIBE FOR money orders should be drawn tu order of EXPERIMENTER PUBLISHING RADIO NEWS. Send your name. address and re- mittance to Experimenter Publishing Co., 230 Fifth Ave., Nov York. Mention CO., INC. name of the magazine the be to you are ordering. We also publish SCIENCE AND INVEN- All communications and contributions to this journal should addressed TION. RADIO LISTENERS' GUIDE. AMAZING STORIES Editor. RADIO NEWS, 230 Fifth Ave.. New York, N. Y. Unaccepted contribu- HUMOR. Write clearly. and FRENCH tions cannot be returned unless full hostage has been Included. All accepted con- tributions are paid for on publication. A special rate is paid for novel expert- RATES AND TERMS. The subscription rate for RADIO NEWS is $2.50 per molts: good photographs accompanying them are highly desirable. year. (12 numbers). When remitting do so by cheek. money order, or registered Entered as second -class matter. Job' 12. 1924. at the letter if cash [s enclosed. Avoid sending cash through the RADIO NEWS. Monthly. serlptfons mail if possible. Sub - l'ost Office at New York, N. Y.. under the Art of March 3, 1879, Additional entry for less than are year are rat accepted. Subscription may be made In at Dunellen, N. J. and San Francisco. Calif. Title registered U. S. Patent Office, combination 'tth SCIENCE & INVENTION. RADIO LISTENERS' GUIDE, Copyright, 1928, by The Experimenter Publishing Co., Inc., 230 Fifth Ave., AMAZING STORIES and FRENCH W \IOR, New York. The contents of this magazine are copyrighted and must not be POSTAGE. We prepay postage in all palis of the United States, without Island possessions. or Mexico and reproduced in the United States giving full credit to the publication. For foreign Canadian subscriptions wo require 50 cents in Translation into foreign languages oust not be made unless permission i+ addition to the subscription Mire tar additional postage charge. obtained from the publishers. Copyrighted In Germany. Reproduction of articles CHANGE Oie ADDRESS. Notify us as far in advance as possible. It reunites In farinamy is reserved for Radio. Berlin 42. several weeks to make an address change on our records. Always write cleari, The contents of RADIO NEWS are indexed in the Industrial Arta Index, copies of which can be found in every Bbrary. General Advertising Dept., 230 Fifth Avenue, New Ytirk City ADVERTISING REPRESENTATIVES L. F. McCLUItE, 720 Cass Street, Chicago, Ill. HARRY HYDE, Drexel Philadelphia. DAVIES, DICTON A KELLY. 15 West 10th St.. Kansas City, Mo. DE, RIS it lin . Calif. 412 West 0th St., Los Angeles, Calif. T. F. MAGR.NE, Park Square Bldg., Boston, Mass. Leary Building. Seattle, Wash.

www.americanradiohistory.com Radio News for April, 1928 1091

Check it with any set you choose! -then hook it up and learn first hand its superior tonal and reception qualities!

SPECIFICATIONS AC BANDBOX 704 ? ?

1. Genuine Ncutrodyne circuit. Yes 2. Alt elements totally shielded. Yes 3. Full 180 volts on plate of output Yes tube. 4. Supplemental tuning devices for Yes hair line alignment of con- or in two units densers to secure sharpest possible tuning (Acumina- for console installation tors). s, Single station selector. Yes at $90 6. Illuminated dial. Tes 7. Volume control that will reduce Yes heavy local reception to a whisper without dctuning and without distortion. 8. Power plant with a condenser Yes of 30 mf capacity. 9. Self- healing condenser. Yes The NEW dry cell 401 10. Modem, neat, compact, richly Yes finished cabinet. Bandbox Junior 11. Adaptability to any type of con- Yes A new dry cell receiver with all the Crosley Banjhns sole cabinet by being available features -selectivity, sensitivity, volume and appear- in single or double units. ance. Ideal for homes having no alternating lighting current or where storage battery service is not avail- 12. Quantity production price of Yes able or desired. Especially desired because of its less than $100. tonomctlinstallation cost and opera- ^ Lion. Batteries ast Use Crosley Musiconc for perfect reproduction!

Battery type Bandbox operating with storage batteries or power supply $55. 1:0 "You're there with a Crosley" Crosley it licensed only for Radio Amateur, Experimental and Broadcast Reception. Montana, Wyoming; Colorado, New Mexico and ¡Vest prices slightly higher. Write Dept. ea for descriptive literature. THE CROSLEY RADIO CORPORATION CINCINNATI, OHIO POWEL CROSLEY, Jr., Pres.

www.americanradiohistory.com 1092 Radio News for April, 1928

INDEX TO ADVERTISERS

Page l' gr Page l'age A D Ii

Abox Co., The 1096 Deutschmann Co.. Tobe 1171 Karas Electric Co. 1180 Radio Equipment Co. 1164 Acme Wire Co. 1163 Knapp Electric Corp 1177 Radio Institute of America 1175 Aero Products, Inc. 1176 E Radio Products Co. 1169 Aerovox Wireless Corp 1185 L Radio Specialty Co. 1192 Elba Products Mfg. Co. 1189 All Radio Co. 1187 Electric Specialty Co. 1171 Lacault Radio Electric Labs., S American Bosch Magneto Corp 1188 R. E. 1160 Engineers' Service Co. 1155 American Mechanical Labs 1180 Lacey & Lacey 1187 Sangamo Electric Co 1159 Erie Fixture Supply Co. 1157 Amrad Corp., The ...._ 1191 Langlein- Kaufman Radio Co , School of Engineering of Mil- The 1172 waukee 1167 F See jay Battery Co 1161 Fanspeaker Radio Co 1185 M Shure Radio Co. 1172 B Fansteel Products Co., Inc. 1159 Silver- Marshall, Inc. 1167 M. & 11. Sporting Goods Co 1189 Ferbend Electric Co. 1191 Smith, B. Hawley 1169 Barawik Co., The ..1159, 1188, 1191 Midwest Radio Corp. 1171 Solderite 1168 Fergus Co., The 1181

Boudette Mfg. Co. - 1159 Muter Co., Leslie F. 1188 Ferranti, Inc. 1187 Starrett .Mfg. Co. 1157 Brady, John 1L. 1187 Formica Insulation Co. 1180 T Burt. Dr. Itou t C. 1159 N Fort Shelby Hotel 1165 Freshman Co., Inc., Chas 1185 National Company, Inc. 1180 Telephone Maintenance Co. 1184 Frost, Inc., Herbert II. 1172 National Radio Institute 1093 Teleplex Co. 1168 1183 Norden-Hauck, Inc. 1153 Thordarson Electric Mfg. Co Mfg. Corp. G North Shore Radio Labs., 1180, 1188 Tower 1167 C. E. Mfg. Co., Inc. 1178 Townsend Laboratories ....1165, 1182 Carborundum Co., The 1157 General Electric Co. 1159 O Tyrman Electric Corp. 1188 Carter Radio General Radio Co. 1171 Co. 1169 U Central Radio Labs. 1189 Omnigraph Mfg. Co. 1167 H Chemical Institute of N. Y , Outdoor Enterprise Co. 1176 Ultradyne Sales Co 1087 Inc. 1095 Hamilton-Carr Radio Corp. 1173 Chicago Radio Apparatus Co. 1181 P w Ilammarlund Mfg. Co. 1169 Chicago Stock Gear Works 1157 Ilammarlund- Roberts, Inc, 1182 Parker, C. L. 1188 Walker Co., The, Geo. \\' 1168 Cloverleaf Mfg. Co. 1168 The 1161 Mfg. Co.. Warren Electric Co. 1171 .Connor llarco Co., Peerless Radio Cabinet Co. 1172 Inside Back Cover West Side Y. M. C.:\. 1164 Consrad Co., Inc., I Potter Products Corp. 1185 Radio Mfg. Co. 1176 1156, 1158, 1170, 1174, 1186 Western Press Guild, Inc. 1179 Whitehall Hotel, 'l'he 1160 Consumers Radio Co. 1178 Illinois Transformer Co., Back Cover World Battery Co. 1160 Craftsman Radio Products 1171 Ltdependent Electric Works 1165 R ('rosley Radio Corp. 1091 J % -Y Cunningham, Inc., E. T.. Radiali Company 1173 Inside Front Cover J -M -P Mfg. Co. 1164 Radio Association of America 1089 N -L Radio Labs. 1173 Curtan Mfg. Co. 1161 Jewell Electrical Inst. Co, 1183 Radio Engineering, Inc. 1154 Yaxley Mfg. Co. 1191 Abeii\liny,s\tecte icathcr bircIirç S. Gernsixick's Radio Ejyc1opedia

most valuable of Radio Books -S. Gernsback's THEEncyclopedia -now the most beautiful. This foremost Radio Encyclopedia is now offered in this luxurious new binding to meet the demand for a more handsomely bound volume. The limp suede leather edition sells for $5.00. The Keratol- leather stiff binding still can be had OO for $2.00. Remember -this is an encyclopedia -not a dictionary! It took over two years of intensive labor to compile it. ERATOL BINDING r It is the first Radio Encyclo- s. pedia ever published. $2. I. 30 pilt.\Sg 1 ta r4 A S. Gernsback's Radio En- t moat °?, oti New cyclopedia contáins the o y / zig, 'a i ;,rÿ meaning of every word and phrase used in the entire sç.OQ payptticott, / ok ede7e SEND Radio Art. Every circuit, part and apparatus is thor- p-afha°eta''Lndln / \ae trtde6foheeP^ßi / N 0 oughly explained. A complete cross index is just one of 6 14CO °dröR / Addy ta J'o,t / MONEY the many features of this remarkable book. a'-0nt) / DOs_n.. .. /simply pay the post- There are 1,930 definitions -549 diagrams,g photo- man on delivery. graphs and drawings -all simple and easily understood. albjn.000cooies in the I ran hiatms keaap solo The book is nearlyY 1 inch thick and measures 9x11 inches. ` _¡ S. GERNSBACK, 230 FIFTH AVENUE, NEW YORK CITY

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Dear Mr. Smith: Kindly send me your big book, "Rich money. -Earle Cummins, 18 Rewards in Radio." giving information on the big -money Webster Street. Haverhill, 1.1ass. opportunities in Radio and your practical method of teach- ing with six big Outfits. I understand this book is free. and that this places me under no obligation whatever. Em 4ment Service to all Goï Name 4ge Address

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www.americanradiohistory.com 1094 Radio CTC'S for April, 1928

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www.americanradiohistory.com Radio News for April, 1928 1095

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595,728 Hours of Actual Operation on 1182 Different Sets Troves neyona All L0UDI the ABOX Claim to Superiority

1182 users of ABOX ELIMINATORS wrote The Abox Company between January 17th and February 10th, 6 -Volt Abox 1928, giving a detailed account of their own experiences Eliminator with the ABOX. All kinds of sets were used in this This model will op- erate any set using test under all conditions. Remember, this is not a eight or less stand- ard 6 -volt tubes. report of a laboratory test, but is a test made in the Not necessary to change set wiring. hands of users like yourself. Over 100,000 of this type in use. The following comments are typical:

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www.americanradiohistory.com GernnsLac.k3 (R Publisher - Editorial and General Offices, 230 Fifth Avenue, New York

Vol. 9 APRIL, 1928 No. 10 Radio News' New Policy By Hugo Gernsback

WHEN the first number of know News was launched in July, Since the radio parts dealers declined from 30,000 to 2,500 in a few 1919, l said as follows : "And here is the platform upon which years, if this decline were allowed to go on, it would soon be impossible RADIO NEWS stands. 1 pledge myself to a strict adherence to every to print RADIO NEWS ; because the manufacturers of the radio material plank : would have no longer an outlet. and the radio constructors and home "First: Only Radio --100rß of it- nothing else. builders would find it impossible to buy materials. It is true that a "Second: An organ for and by the amateur. The amateur's likes and wants builder can wind his own coils, and drill his own panels; but certain will always conic first in this magazine. articles, such as switches, condensers, tubes, sockets and others, he can "Third: Absolute Independence. RADIO NEWS has only one Boss -its never hope to make, and must !My. readers. This magazine is not, nor will it ever be, affiliated with any stifling, Against its better judgment. RADIO NEws, during 1927, endeavored to commercial radio interests whatsoever. conditions by publishing names giving '-Fourth: Truth-first, last and always. When you see it in RADIO NEWS better trade manufacturers' and you may be sure that it is so. Not being affiliated with commercial radio inter- manufacturers' specifications in its text pages; because it seemed that ests, this magazine will have no reason to suppress important articles, dis- it would thus be made easier for the reader to buy suitable material than coveries, etc. if no names were given and he had to guess them. In doing so, Reno "Fifth: RADIO NEws iS and will be the sworn enemy of all adverse and NEws honestly believed that not only would it serve its readers, as it unfair radio legislation. had always done, but the radio trade as well. "Sixth: Instructive first and last. Up -to -date sci- It is, however, admitted now that this policy entific articles for your instruction will always have was wrong and, beginning with this issue, we re- first place in RADIO NEWS. We shall publish purely scientific vert to our former custom of not mentioning any articles every month, articles that on account THE articles in RADIO Nsws arc in manufacturers' naines or trademarks of parts and of their length are often crowded out of other my opinion "inspired- by ad- publications. your circuits of any kind in the text pages of RAUto vertisers and of little value to your NEWS. Seventh: First in print with the news. You will 3 radio magazines are Ili that respect, we go back to our for- find subscribers. /ost all important radio news in this magazine front similarly unreliable. ll'hy don't you mer practice of the years previous to 1927. one to three months ahead of all other publications- It was soon found that readers of RADIO NEWS always." occasionally publish something worth while? Your readers arc not all mo- became suspicious and thought that advertisers That was before the days of broadcasting and rater. !l'hea and if you publish a radio were controlling the text pages; and it must be when radio fans still Were "bugs" and transmit- magazine for the benefit of your .al,- admitted that that is the way it often looked to ting amateurs; but, as a whole, the situation has scribers rather than your advertisers, 1 the outsider. not changed, nor has the platform of RADIO will again .vu bscribe. (f'ho :vents a At no time, however, did RADIO NEws reap NEws changed at all. catalog? any material benefit front specifying manufac- On the other hand, in art that as turers' names and materials. If any proof is an grows 17,M ES truly. rapidly as radio, changes occur overnight and it eery wanted, the constant advertising shrinkage of is necessary for any organization, whether a pub- FRANK 11, CHASE, M.1)., RAmo NEWS during 1927 is glowing testimony lisher or a factory, to conform itself to those 2362 W. 21st street. of this fact. At no time did the trade (par- changes. For instance, in 1919 there were some Los Angeles, Calif. ticularly the parts manufacturers) really support 10,000 amateurs, and not one of the' so- called RADIO NEws, in spite. of its publishing their "broadcast fans," because there was yet no names and specifications quite freely. An in- broadcasting. tolerable situation was reached, since it was im- When broadcasting came along, it meant an important change, not possible to mention in one issue the products of all manufacturers and, only to the amateurs and fans, but to the radio industry as a whole. wherever one friend was made among the parts manufacturers, many Changes came about with lightning rapidity, yet RnDIO NEWS adapted enemies were made. itself to them to give the maximum service, not only to its readers, but But the worst part was that many readers became dissatisfied with to the whole industry as well. seeing so many circuits, which to them seemed sponsored by kit manu- RADIO News has always been the largest of all the radio publications facturers; and some refused to read RADIO NEWS any longer. Letters in point of circulation, and otherwise; and as such, it has a tremendous like that printed here became numerous as time went on. obligation to. not only the radio art itself, but all interests connected Yet it must be evident to every fair- minded reader that the publishers with it- readers. fans, amateurs or the industry. As the strongest and did not reap a harvest from the manufacturers. Quite to the contrary, most representative of all the radio publications, Rnuio NEws has always the publishers lost heavily during the experiment. So, beginning with valiantly striven to be of service to all concerned. this issue, we revert to our former rule, as follows: From 1919 to 1926, it was the policy of RADIO NEws never to mention RADto NEWS will no longer mention any radio material by a trade- the name of any product within its text pages. RADIO NEWS has always marked name; no manufacturers' navies will be printed in an article on maintained that the proper place to advertise a product is in the adver- construction. Circuits originated by parts and kit manufacturers will tising pages rather than in the text pages. However, toward the end of not be given the manufacturers' naines; if a worth- while circuit comes 1926, it was seen that the radio parts industry was heading rapidly along, RADIO NEWS will bestow on it its own proper name. downward ; and it became necessary. as it had been necessary before An important new policy will be initiated, under which RADIO NEws during similar changes, to recognize the altered conditions. During the will give away free the blueprints that. for over two years, have been radio boom, there were some 30,000 dealers in this country handling sold for from $1.00 to $2.00. These blueprints with full specifications radio parts ; at the end of 1926, this number had shrunk to no more will. however, contain the names of the parts which were used by the than 2,500. constructor who designed the actual assembly. On the blueprint will be RADIO NEWS then was confronted with a most perplexing and diffi- mentioned the trade name and the manufacturers' names, so that the cult problem. Its readers always had been amateurs. fans. and construc- constructor who wishes to build the circuit can do so with the least tors who built their own, as well as custom builders. For that reason. amount of difficulty. But this information, as we have said, will not be ninny new and novel circuits were published in RADIO NEWS, such as published in the text pages of Lunn NEWS. the Tropadyne, Ultradyne, Strobodyne. Intel-flex, and many others of In all other respects RADIO NEWS' policy will be the same, except that national and international importance. But RADIO NEWS also recog- hereafter only one featured constructional article will be published each nized the obligation to see to it that the' man who wanted to build his month. This does not exclude the publication of constructional articles own could do so. This. of course, is elementary; if you write a book on for beginners, describing circuits in which not more than three tubes bridge. and it becomes impossible for the readers of that book to buy are used. There will, therefore, he not more than two constructional playing cards, the book is useless. If you publish a golf magazine and articles describing receivers in RADIO NEWS monthly, although there it is impossible for the readers to buy golf clubs and golf balls anywhere may be an occasional description of a power pack, amplifier, etc. in the country, you will not stay in business long; neither will a publica- It is hoped that, in making these changes, RADIO NEws will continue tion advance the golf industry if it does not help create markets for the to serve, as before, the entire radio industry ; but. first and always, it golf manufacturers. All this is self -evident; RADIO NEws is in a posi- should be understood that R.4nio NEWS is published primarily for its tion not at all different. readers. That has always been its policy, and always will.

Mr. Hugo Gernsback speaks every Tuesday at 9.30 P. M. from Stations WRNY (326 meters) and 23EAL (30.90 meters) on various radio and scientific subjects. 1097

www.americanradiohistory.com 109.5 Radio News for April, 1928

ACK a few years -and not so very limitations of space, with respect to sound. Although the picture as seen in the tele- many at that -it was said that but Is it now considered marvelous when a vision receiver appears no more than three one human faculty could jump in singer is heard, three thousand miles dis- inches square, and there are instants when 13 a fraction of a second from one end tant? Indeed, no; the listeners take it as it is obliterated 1w static or some other of the earth to the other-the imagination. a matter of course, as they do the other interference, the remarkable part of the Up to a comparatively short time ago this wonderful inventions in daily use. story is that the device worked at all: Every was true; but, with the advent of radio But until very recently it was still up to so often, during the last few years, enthu- broadcasting as it is known today, it be- the overworked imagination to picture the siastic articles have appeared, telling how came possible practically to annihilate the appearance of the performer who was television is rapidly becoming a reality in- broadcasting. In some stead of an engineer's dream. But these cases this may have been fulfillments of dreams were in laboratories; for the best; as the now television has been carried to the house. imagination is a wonder- ful artist, and produces TELEVISION DEMONSTRATION often beauty where In one corner of a vast room in the beauty is not. But, for General Electric Company's research labora- better or for worse, tory at Schenectady, N. Y., a few days ago, thanks to the further de- were set up an arc light, a rapidly-revolving velopments made by Dr. metal disc, four photoelectric cells in a E. F. W. Alexanderson frame, and several boxes. Just around a in the art of television, corner a group of men were gathered in a what actually occurs in room totally dark, save for two squares of the broadcast studio can pinkish light about three inches square. now be seen by the radio These two squares of light were the cyno- audience. sure of all eyes; these pinkish squares were what many of the men in that room had At the top of the page, hating travelled hundreds of miles to see; for they the television receiver: the image is .seen through the were the proof that television in the home small square opening on a is no longer a dream, but an actual fact. level with the operators' eyes. Notice the broadcast receiver A young woman was seated before the and loud speaker. At the bank of photoelectric cells, with narrow left, Fi-a. D. shows the rear of the receiver: one man is bands of light and shadow playing across pointing out the universal her features. She smiled, frowned, rolled motor, which drives the scam sting disc. Above the motor bet. eyes, and smoked a cigarette -and all is the Moore neon lamp. On these acticais were instantly and faithfully the lower shelves are bat- teries and the amplifier and pictured in the little squares of pinkish light rectifier tubes. Dr. E. F. W. in the adjoining dark room. At the same Alexanderson is seiii at the left in each illustration. time, the conversation which she kept up with one of the operators came into the dark room through a loud speaker. Then

www.americanradiohistory.com Radio News for April, 1928 1099 her place was taken by a young man with After the rays of light from the arc have peared in Ram NEWS, from December, 19.25, a ukelele and, although the instrument was been broken up by the revolving disc and to May, 1926), is that it responds to the invisible (being below the line of vision of focused on the face of the subject (where changes in intensities of the current and the transmitting apparatus), his voice and they appear to the camera as a series of causes fluctuations in the intensity of the the music cause from the loud speaker as light and dark lines; see Fig. C), they are emitted light; just as the diaphragm of a his face appeared in the magic squares. reflected from the surface of the face to loud speaker produces pulsations in the air The question will present itself naturally the four photoelectric cells in the thick, in response to alternating- current impulses. to the reader's mind: "How well did these square frame of galvanized iron. These It is said that this lamp will go on and off faces come over the air ?" It was possible possess the property of changing light en- in a millionth of a second; so that in its to see every detail in the features, the in- ergy into electric energy. (These cells were dividual teeth, for example; when the eyes described on page 640 of the December, were rolled, one could follow with ease the 1927, issue of R.wto NEWS; previous tele- movement of the pupils: In short, the vision Experiments will be found described transmission of faces by radio can be com- in the June, 1927, issue.) The output of pared in quality to moving pictures in their these cells, after being amplified, modulates earliest days. the carrier wave of the 37.8 -meter trans- In three homes in different sections of mitter, the antenna of which is located on Schenectady, similar television receivers had the roof of the research laboratory. In been installed to show that reception in the Fig. B may also be seen at the right of the home is possible and practicable. A short table the condenser microphone for picking antenna was employed to pick up the 37.8 - up the voice, which was simultaneously meter wave on which the television impulses broadcast on R'GT's regular wave of 379.5 were broadcast. The results obtained in meters. A very short wavelength was chosen the homes were of the same excellence as for broadcasting these "pictures" because those demonstrated in the laboratory. a channel 40 kilocycles wide is needed; this D. 11cFa,lan Moore (left) and E. F. IV. is because of the depth of modulation neces- Aleranderson discussing Nie nean lamp used in THE ELECTRIC EYE sitated by the great range of differences in the television receiver The transmitting apparatus for broadcast- shading, which must be reproduced in the ing television is not very complicated, as transmission of vision. can be seen from Figs. A and B, which show use there is none of the "tinie lag," 'which ' THE ELECTRIC PAINTBRUSH time pick -up. In the left fffleground of Fig. is the greatest problem those working in A is a powerful arc light, the rays of which 'l'he average radio enthusiast is most likely television have liad to meet. are broken up by the spirally -arranged boles much more interested in the apparatus. for The plate of the Moore tube, on which in the disc, which is rotating at the rate reception than in that just described. Com- the image is built up, is about 11/2 inches of eighteen revolutions per second, being pared with the television receivers that have long and 1 inch wide. The scanning disc, driven by a small motor. The light rays been described in this magazine previously, which can be seen in front of the lamp in are concentrated and focused on the face the latest one is simplicity itself. In place the rear view of the apparatus (Fig. D), of the girl by means of the lens held in the of the loud speaker, a Moore neon tube is of the same size as that used in the trans- square wooden support. See Fig. B. is connected in the output of a short -wave mitter, 24 inches in diameter. The 48 holes receiver of the re- (which have a diameter of 35 mils each -or generative type. about 1/30 -inch) trace successive lines on The most inter- the picture, literally "painting" it in one esting property revolution. The disc is turned by a stanu- of the neon lamp, ard "universal" motor; which is to say that which was in- it can be operated from either direct or vented by D. Mc- alternating current. The speed of this.ifiotór Farlan Moore (as and, therefore, of the disc, is controlled by related in Mr. a push- button. In order to enlarge the Mooré s biogra- image as much as possible, a magnifying lens p h y, "Thirty is placed between the scanning disc and the years in the Dark observer's eye; thus bringing the image up Room," which ap- to 3 inches square.

Fig. A at the left and Fig. B below show the relative positions of the ap.. paratus used in transmitting by radio the image of the girl. In Fig. A the arc lamp is at the left and, between the revolving disc and the square frame holding the photoelectric cells, is Na small square ::ooder holder carrying flu. lams. The amplifier is in the two boxes at the right.' Time grouping of the photoehetric cells is shown in Fig. B belon', three bring visible and a fourth behind the amplifier bares. Note the min'ofhone at the right and the lines of light and shadow on the girl's fare in Fig. B; and the enlargement in Fig. C, at the lower left.

www.americanradiohistory.com 1.100 Radio News for April, 1928

WAVE MOORE ARC LIGHT PHOTO - ELECTRIC SHORT- CELLS RECEIVER NEON LAMP AND AMPLIFIER, LENS et/ 37 i

I`

DRIVING MOTOR - -- MICROPHONE TRANSMITTER UNIVERSAL OPERATING ON MOTOR 37.77 METERS AT- RESEARCH SCANNING LABORATORY, ,,,7,p¡1. DISC SCHENECTADY

! BROADCAST LOUD \. AM PLI FI ER = RECEIVER SPEAKER

WGY TRANSM TTER TRANSMITTER AT 379.9 METERS SOUTH SCHENECTADY

A diagram of the Alexanderson method of operation in the transmission image and the microphone for the voice, which is broadcast on a different and reception of television. At the upper left are the transmitter for the wavelength. At the right are the receivers for television and speech.

SYNCIIRONIZATION BY HAND tubes. A storage battery and dry -cell "11" saute status that voice transmission has batteries for the short -wave unit are on a today. Of course, there are still a number In most of the television receivers built shelf over this amplifier, which utilizes A.C. of "hugs" that have to be eliminated before heretofore, there has been employed some house current. By the use of a universal the apparatus can be put on the market automatic means of synchronizing the re- motor and the rest of the equipment as for general use; but, considering the rate ceiver with the transmitter; such as the mentioned above, it may be easily seen that at which television engineers are progressing broadcasting of a certain frequency that the television receiver is one that can be in their work, the time is approaching would make two motors run at exactly the used in almost any home; the only provision rapidly when it will be possible to see as same speed. In Dr. Alexanderson's system being that 110 volts of either A.C. or D.C. well as hear the artists as they appear in no such of synchroniza- complicated method be available. the studio. (Continued on page 1156) tion is employed; the simple and only speed control is a push -button that varies the NEW DISCOVERIES IN RADIO speed of the universal motor turning the disc. When introducing his apparatus in preparation for the demonstra- When the receiver is first started the tion, Dr. Alexanderson mentioned speed of its motor is far below that of the the fact that he expects televis- one at the transmitter, and the resultant ion to have within five years the image is a straight line of light. As the motor is brought nearer and nearer to syn- chronous speed, this line of light breaks up into a series of parallel lines, slanting first Fig. E. The new type of short -wave one way and then the other. Then there transmitting antenna, called the "checker- appears a distorted image of a face, again board." The sides of each square are breaking up into splotches of light and dark. equal to one -half a wavelength. These Finally, when the two motors are running half-wave antennas arc so connected in synchronism, a true image may be seen that they oscillate in phase and need not on the lens. This image constantly shifts be turned. from one side to the other, as the speeds of the two motors vary; but this shifting from side to side does not interfere with the re- ception, as the movement can be made to be very slow. Here it is that the operator must exercise his skill, in keeping the received image as near the centre of the lens as possible. This is done by "whipping" the motor; i.e., send- ing an electric impulse to the motor by means of the push- button, and thereby in- creasing the speed. This is far from being a difficult feat, as it requires no more skill than steering an automobile along a road. Sometimes, when the two motors get slightly out of synchronism, the lower half of the image may be above the upper; so that a man's collar and tie may be seen above his head. This condition can be easily adjusted, however; just as n like condition is remedied by the motion -picture operator when the picture gets out of its "frame." In the lower part of the cabinet, which (as may be seen) is about the same size as that which houses an ordinary talking ma- chine, is an amplifier with two rectifier

www.americanradiohistory.com Radio News for April, 1928

Fig. A. The apparatus for receiving photographs by radio, fast ailed in the horse of Dr. Alfred N. Goldsmith in New York City.

NOT quite two weeks after "tele- at the left is the original and the oilier the and the scanning disc to the photoelectric vision in the hone" had been suc- picture after it was developed in Dr. Gold- cell. (See Fig. 1.) cessfully demonstrated in Schenec- smith's home. The rapidly- revolving disc, at tin front tady, N. Y., the transmission of end of the case containing the photoelectric photographs by radio and their reception TILE PHOTOGRAPHIC PICK -UP cell, has around- its circumference a srries of in the home was exhibited be the National In Figs. B and C are shown two views of indentations or notches. These notches in- Broadcasting Company in New York City. the pick -up apparatus in the studio. Fig. terrupt the light rays at a certain frrquencs Dr. E. F. W. Alex: nderson, consulting en- B shows E. C. Ballentinc placing a photo- and the photoelectric cell is energizc.1, every gineer of the General Electric Company, is graph of D. McFarlan Moore, the inventor so often, by n reflected ray of an intensity credited also with the development of this of the neon tube used in the receiver, on which depends upon the depth of shuck is simplified system for receiving pictures with the cylinder. In Fig. C the synchronous the minute area of the photograph the. apparatus that can he connected in the out- motor in the foreground turns the cylinder being reflected. These variations of light put of an ordinary receiving set. The pic- a a constant speed, properly reduced by are translated into electrical impulses by tures were broadcast on \\'EAF's regular the gears. A source of light is concentrated the photoelectric cell and after being ampli- wavelength of 492 meters. on a small portion of the photograph, this fied are put on the air as a modulation of The apparatus demonstrated by Dr. Alex- small area reflecting the light through a lens the carrier wave. andcrson is far from complicated, yet it does not sccou quite as simple as the receiver for picking. up television broadcasts. The transmitting apparatus was installed in a studio of the National Broadcasting Com- pany, at iIh Street and Fifth Avenue, New York ('ity. A photograph of the mayor of the city. the ):Ion. James J. Walker, was clamped around the cylinder of the trans- mitter, as shown in Fig. B. As the cylinder is turned by a synchron- ous motor at a constant speed, a photo- electric cell, contained in the box next to the wall, transforms the light energy into electrical energy. The light is reflected to the cell from the surface of the photograph and is broken up by the revolving disc, which has a slotted edge. The output of the photoelectric cell is augvlifted and is connected to the regular broadcast trans- mitter, in this case at Bellmore, L. I., by means of land lines. At the WEAF trans- mitter the picture was put on the air, and received in the home of Dr. Alfred Gold- smith at 82nd St. and West End Ave., New York, (See Fig. A), a distance of approxi- mately twenty -five miles. The results of At the left is an vuretouohed reproduvrtion of an original photograph of Jessica this transmission, which took about 90 sec- 1)ragonette, 11rEAF artist, and at the right the anaretourhed picture. as it roar rpreired onds, are shown in Fig. 1). The photograph in Dr. Goldsmith's homy.

www.americanradiohistory.com Radio News for April, 1928

broadcast receiver. This is tuned to a sta- tion which is transmitting the pictures, in the same manner as though music were to be heard. Instead of the loud speaker the apparatus shown in Figs. E and F is con- nected to the output terminals of the set. In Fig. E Dr. Alexanderson is shown be- side the receiving apparatus, from which the cover has been removed. The sheet of bromide photographic paper is wrapped around the cylinder, preparatory to receiv- ing a picture. This paper must, of course, be protected from the light of the room, until after its exposure to the light con- trolled by the incoming radio signal; this protection is afforded by a light -proof cover, which is shown in position in Figs. A and F. Standing open against the wall is the shielded box containing the amplifier, which strengthens the impulses before they are sent to the neon lamp. This lamp, which operates on the saine principle as the one used in the television apparatus, was also developed by D. Mc- Farlan Moore. Instead of the tube's hav- Fig. E. hr. E. E. ti- ..,Ii.randerson is here shown beside his receiving apparatus. At ing a plate on which the images are built the rear of the table is the special amplifier and, in the foreground, the receiver with up, its central electrode is a rod, in which the revolving cylinder exposed. there is a small crater. By the variations in light intensity produced by the neon lamp the light and dark portions of the photo- The ordinary transmitting equipment of process. The picture shown in Fig. D was graph are faithfully printed on the sheet the station is used, the only substitution transmitted in about one minute and a half, of photographic paper, on which they are being that of the photographic pick -up for a rate about twenty times as fast as that focused by a lens. (See Fig. G.) the microphone. Ordinary land -line, or "re- of other processes. The cylinder is driven by a synchronous mote control," is employed as usual. One motor and gears, similar to those at the of the most important things that Dr. Alex - TifE RECEIVING EQUIPMENT transmitter. As the cylinder revolves, it anderson lias done, besides simplifying the One of the first requirements for receiv- also moves along a threaded rod, thus ex- apparatus, is the speeding up of the entire ing pictures from the air is an ordinary posing the entire sheet of sensitive paper

C shows at the left the notched disc, whine breaks up Fin. B, below: E. C. Ballentine the reflected light , -ays (produced placing a photograph on the cylin- by the lamp in front of the disc der preparatory to transmitting it and reflected from the picture on aver 7T-E.lF. Fin. D, in the cen- the cylinder), before st reaches ter, is a reproduction of an t.,t- the photc cicrtric cell, located in retouched photograph of Mayor the bas- behind the disc. The James J. Walker, of New York motor at the right turns the City, before and after transmis- cylinder. sion over the radio.

www.americanradiohistory.com Radio Ncws for April, 1928 1103

BROADCAST GEARS ANTENNA

PICTURE DRUM MOTOR LENS TRANSMITTER IMAGE FROM PICTURE LIGHT MOORE j,MOTOR LOUD LAMP WINDOW -fit --REVOLVING DISC SPEAKER CYLINDER WITH LIGHT SENSITIVE NEGAT;VE PHOTO ELECTRIC AMPLIFIER CELL

RECOVER 1111 uj,nuam immmni -, ,L94Q90, f, (000000) b boDoti) TRANSFORMER DETECTOR TUBES

FIG. 1

The diagram illustrates the process through which a photo- it is finally receiver/ on the cylinder on toe rigid, it must be graph goes when being transmitted through the ether. When `developed" and "fired" as with an ordinary print. to the light rays. Before the actual trans- loud speaker at the receiving end. A. milli- the correct intensity strength for tone mission of the photograph takes place, in- mnmeter on the box containing the amplifier shades. These adjustments are easily and suctions from the transmitting station are indicates to the receiving operator when his quickly nhnde. After entire surface of broadcast and received through the regular receiver is properly "framed" and set to the paper has been exposed to the rays of

Fig. P, below. lir. .1(eranderson in his laboratory adjusting the receiver. Fig. G, on the right, shows the Moore neon lamp be- ing placed in its brass container on the rear of the cylinder cabinet. Note the simplicity of apparatus.

the Moore lamp, the picture is developed mld fixed, ,just as in the case of an ordinary photographic contact print.

STATE Or TIIE ART What this phase of broadcasting will do, for the art as a whole, is still a platter for conjecture. Officials of the National Broad- casting Company, when questioned at the time of the demonstration, refused even to guess when regular transmissions of this nature would be inaugurated. They stated, however, that a possibility of its use is the broadcasting of II printed program each day, so that listeners may be able to know when certain features will be on the air. 'l'bis (Continued on page 1163)

www.americanradiohistory.com 11U4 Radio News for April, 1928

"Chains and Slavery" when he is giving the N. B. C. and chain what I have to work with, I'm not so bad programs "Hail Columbia." Personally, I at that. Editor, RADIO NEws: prefer a chain program any time to his and Since the first of December, and I only When the hat is passed for that big col- others in his class, such as W. K. Hender- try one or two nights every two weeks, I lection that Geo. W. Pangborn advocates, son, continually finding something to gripe have logged 142 stations, and WRNY was don't Stop there. Who would want to pay about. I suppose they want to monopolize the 142nd. Have been fishing for you some for some of the jumbled -up mess that some- the air with "Canned food for sale," "Horse time, and last night (January 17), at 9:45 times comes via independent and network collars," and canned music. Central 'Time, your station came in good stations? would Where there be any justice I can truthfully say 90% of the pro- and clear and with good volume. I am in letting listeners decide what stations that grams I get are chain programs -that is, using a four -tube regenerative set (R. C. A. should be allowed freedom of the air? The with model 10 speaker.) I have also a big network that he advocates would be a Radiola 2.5, but can get better results with rank injustice unless all were forced to go the regenerative. on one wavelength -which is very plausible. E. T. BATES, Patents have been issued for that purpose, A New Addition to Plerna, Alabama. but where have they gone? I am opposed RADIO NEWS to any desire to permit a furtherance of SINCE this magazine was estab- the chain; there are too many chain sta- lished in 1919, it has become the tions now occupying a number of channels Not a Man's Job most important in the radio field in. with- the same progrm. Nightly there are RADIO NEWS: this country, if not in the world. Editor, 25 stations in one chain. Formerly we had I wonder if the women wouldn't all like RADIO NEWS has been read, not only a diversity of 25 different programs from (I know I would) to hear more lullabies radio amateur, set builder those stations -who cares whether it is by the the sung over the radio by women singers in- the highly -paid artists from New York that and the set owner, but by practically stead of men. entertain us? Many times I have thought everyone who is interested in radio. Of course, it's fine to hear men sing that undiscovered nincompoops provided More than 30,000 of these readers are lullabies, but in real home life it's the better entertainment than those headliners radio manufacturers, distributors, women who sing most of them, and the men played by the chains. Let freedom of the jobbers and retailers. So great has s really seem to be intruding on babies' and air go unchallenged. I'm sorry I am not been the growth of this circulation, women's rights in singing them so much n business man, but I am down among that it has been found necessary to on the air. I'm afraid the lullabies they those wage earners where money counts. issue a trade section of this magazine, sing to "Mike" would only arouse the wrath W. M. BROWN, to be known as of the baby, and it would probably join Germantown., Ohio. lustily in the chorus. Radio News Although it is nice to see a man take Dealers Personal Edition an interest in his infant, the chances are (Few subjects seem to arouse deeper feel- that his singing of a lullaby in the home ings among radio listeners than the questicn This section is for the radio trade would be a forced transaction, and not very of chain broadcasting. Many of our readers, ONLY, as its entire contents will be soothing. especially in the Middle West, condemn of interest to those who are in the So lets hear more lullabies sung by women, Chem bitterly, and advocate "one program, radio business, but not to anyone who so that our minds may picture a baby with one channel." Yet, as stated by the Radio is deriving his livelihood from other sweet drooping eyelids. Commission, the larger stations show more activities. For this reason, it will not MRS. H. GERSTEN, and more tendency to affiliate themselves be put on sale at the newsstands, but 900 Oakdale Avenue, with these costly programs, and the head- distributed solely through the snail to Chicago, Illinois. liner talent they furnish. Many appeals the radio trade. have been made for a poll of listener,pref- The publishers will be only too glad erences; and, while it would be impossible to send you, without charge, a copy of for Every Flight to publish all the individual expressions of the new DEALERS PERSONAL Radio opinion, RADIO News will be glad to tabu- EDITION, if you are a radio. manu- Editor, RADIO NEws: late those for and against the present situ- facturer, distributor, wholesaler or re- With reference to the recent catastrophe, ation. On the side of the network enter- tailer. You can obtain it only by ask- the loss of Mrs. Frances Grayson and com- tainment, we give the following letter from ing for it YOUR BUSINESS panions in her transatlantic plane "Dawn," -ON would publish, a reader who is thankful for the excellent LETTERHEAD -and you are cor- I would appreciate it if you entertainment with which he is favored. dially invited to do so. See page 1176 in your excellent magazine, a suggestion to - the EDITOR.) of this issue, and future transatlantic fliers, and general public, regarding the danger of inadequate heretofore used on trans- WRITE FOR YOUR COPY radio equipment, NOW! atlantic flights, and lack of trained radio- "They Satisfy" men, which is partly responsible for the Editor, RADIO NEws: complete disappearance of several planes I like to read the different opinions as and their occupants. to the operation and control of broadcast- at night. The reason, of course, is that they To give an instance of the value of radio ing. Some, in my opinion, are good; while are better than others, and I can't see any on these flights, I will quote the case of I think others have about as good ideas as special benefit that it would be to the small Commander Byrd's successful flight from I would have should I undertake to stations that are fighting the chain pro- New York to Paris in "Miss America." Of straighten out the air waves, so to speak. grams to have all the latter on one wave. all the planes, that have flown, or have at- Your editorials and such articles as I I am quite a DX hound; at least I think tempted to fly the North Atlantic, I believe find on pages 869 and 871 of the February I am until someone writes you what they his plane was the best equipped in the case issue are very interesting. It is very amus- are doing, and then I find I haven't gone of a forced landing. ing to listen in on Norman Baker of KTNT so far. However, you will think that, from (Continued on page 1187)

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Above is the tanned ship "Antinoe" as seen from the rescuing .4meri- stand -by in a raaiug gale for four days, until the crew of the British can liner "President Roosevelt," which was summoned by an SOS to vessel could be saved. © Herbert Photos.

you ever tune -in on the radio clots of distress flash in from the sea? It tress signals from ships. Such stations are and find it "dead" for no apparent matters not who is facing the microphone, required to keep a licensed radio operator reason? The tubes burn in all their whether it be a staff bedtime -story teller or listening in on tt wavelengths designated DIDglory, but all is silent. You rush $67,000 worth of talent-the SOS has the for distress calls, during the entire period to the roof to see if the aerial is still there. right of way! while the broadcast transmitter is in op- Then you test the batteries; the voltmeter An SOS does not necessarily suspend the eration. needle jumps to a high mark. Well, you activities of all broadcast transmitters. The Every radio station on shipboard must be do about everything imaginable in an effort "key" stations of the radio "chains," as equipped to transmit distress calls on the to bring back the music, but every diagnosis they are on the Atlantic seaboard, may go frequency or wavelength specified by the fails. Why is. the set "dead"? A radio off the air; but the program is sent out licensing authority, with apparatus capable service man will have to perform an au- over the wire lines to the inland network, of transmitting and receiving messages over topsy. It is Sunday, of course; the radio unaffected by the call from the sea. In a distance of at least 100 miles by day or store is closed, so the "doctor" cannot be fact the artists continue to entertain bliss- night. When sending signals of distress, the summoned until morning. 'rhe home seems fully unaware that an SOS has greatly re- transmitting set may be adjusted in such a "lost" without its radio! duced their audience. manner as to product "a marimum of radia- So you decide to go out to the movies, When an SOS silences broadcasters along tion irrespective of the amount of interfer- but you don't enjoy the show because, all the Atlantic seaboard at night, it opens up ence which may be caused." the time, there is that tingle in your brain for the DX fan an excellent opportunity The radio law stipulates that, "All radio that such a fine radio set as yours cannot to tune for the elusive waves of distant sta- stations, including government stations and have anything wrong with it. It never tions. An SOS clears the New York air stations on board foreign vessels when failed before. No one was tinkering with for broadcast reception, like the arrival of within the territorial waters of the United it. An what makes it more aggravating midnight when many of the eastern an- States, shall give absolute priority to radio is the fact that there is absolutely no symp- nouncers bid their audience good-night. communications or signals relating to ships tom of anything out of order. You reason It is seldom that such broadcasters as in distress; shall cease all sending on fre- it all out in the movie theatre. At 10:30 KDKA, Pittsburgh, and others west of the quencies or wavelengths which will interfere you return home determined to perfonn the smoky city sign off because of an SOS. But with hearing a radio communication or sig- autopsy on the receiving set yourself. The the fifty -two transmitters nestled in the nal of distress, and, except when engaged in switch is snapped and-lo and behold -the metropolitan area of New York go off the answering or aiding the ship in distress, loud speaker pours forth its music! What air immediately; because the big transmit- shall refrain from sending any radio com- a grand and glorious feeling! ter known as WNY at Bush Terminal, in munications or signals until there is assur- But what could have been the trouble? Brooklyn, N. Y., or that of NAH'at the ance that no interference will he caused with The next morning you read in the paper Brooklyn Navy Yard instantly endeavors to the radio communications or signals relat- that "An SOS silenced broadcasting for an calm the ether and establish communication ing thereto, and shall assist the vessel in half hour last night." The moral is -when with the ship in distress, or with other ves- distress, so far as possible, by complying the radio set goes "dead," have more con- sels in the immediate vicinity. A 2- kilowatt with its instructions." fidence in it. Call up a neighbor and see "spark" transmitter is used at such times, So while you are sitting comfortably at if his loud speaker is silent too, before you because it radiates a much broader wave home enjoying the Goldman band, the Edi- become "expert" and begin the hunt for than a vacuum -tube outfit and, therefore, is son String Ensemble or the New York Phil- trouble. When a radio set owner begins more likely to be intercepted by a greater harmonic Orchestra, just picture the licensed to look for trouble he will find it, or, more number of stations when it broadcasts radio operator on his tiresome watch, wear- precisely, create it, nine times out of ten. "QRT (stop transmitting), ship in distress." ing the headphones connected to a set tuned An SOS applies the most exacting test of to the 600-meter wave, not so far above the THE RIGHT OF WAY the confidence you have in your receiver. broadcast hand. What does this man do if The Federal Radio Commission is au- he hears the three dots, three dashes and THE PROGRAMS GO ON thdrised to designate radio stations the com- three more dots? But what happens in a hroàdcast studio munications of which are liable to interfere When a radio watchman in the New York when the three dots, three dashes and three with the transmission or reception of dis- area hears a plea for assistance, he first

www.americanradiohistory.com Radio News for April, 1928 1109 verifies it by telephone with the District broadly -tuned signals will penetrate into the gested the adoption of "SSSD1)1)." All Communications Superintendent of the Navy upper reaches of the broadcast band. agreed that such a call was needed but the Department in the Whitehall Building, Usually, one shore station will direct the choice was left to a special conference. which is in constant touch with the Brook- rescue, and within a short time this station Shortly after the Marconi Company insti- lyn Navy Yard station, NAH. will have communicated with vessels close tuted "CQD." to the ship in need of assistance. In com- Erroneously, "CQD" was translated by THE CODE SIGNALS municating with the coast station, ships first the public to mean "Come Quick, Danger." Many times, before the watchman at the ascertain the position of the disabled ves- It was one of the signals radio adopted from broadcast transmitter has had time to verify sel and then report their distance from the the land telegraph which, because of its the call with the District Communications ship in hours. One or two vessels will be higher state of development, was governed office, NAH flashes "QST DE NAH QR7' assigned to speed to the rescue and, once by rules formulated and established by an SOS -meaning, in the parlance of (lots and " they have changed their courses, the "All international convention. Among the tele- dashes, "General Call from NAH, clear the clear" signal, which is two clots- space-dot, graph rules was the authorization of a group air becalms of an SOS!" This is an order is sent out by the hind station and broad- of double- letter symbols used by operators to all stations in the district to sign -off, casting is resumed. to abbreviate and speed -up traffic. be shore whether they broadcasters; ship or "Q," being one of the least -used letters this call is transmitters. When heard-or EARLY DAYS OF "WIRELESS" in the English alphabet, is distinctive and before that time, in the case of an SOS can be recognised easily. The call "Or on which has been intercepted by the watch- Do you know the evolut of the cryptic "SOS" that silences your radio? It really a railroad or commercial telegraph line man and verified by the District Conamuni- means that the operator sending it desires cations office -the operator at the broadcast begins with the first marine accident to be reported by "wireless," on April 28, 1899 all other operators along the wire to listen transmitter immediately tips a little switch to his message. When radio adopted "CQ," which cuts the station's program from the (long before the days of broadcasting), when the steamer R. F. Mathews collided it took the meaning "atop mending and air. Then speaking into a microphone, he listen." Alone, it is important but no cause announces that the station is signing off with the East Goodwin Sands Lightship, off the coast of England. The call for help for immediate alarm. But, in the earl- days because of an SOS. The transmitter is silent, radio, the operator followed the was picked up by a shore station twelve of if 'CQ" but the tubes are kept burning because, gen- with the letter "D^- -'the, signal of danger erally within a short time, the air will be miles away and a rescue party was dis- and distress -it became a. message of gen- clear again. patched to the scene of the wreck, reaching it in time to save all lives. This proved the eral alarm. In the meantime, code transmitters from So harmless is the "CQ," without the "D," Cape Race to Key West are endeavoring to value of radio at sea, and revealed the neces- that even today it is a= custom among disabled vessel, using sity of an international distress signal which communicate with the amateurs and commercial operators to send this purpose every the power could he understood easily by the operators for fraction of "CQ" in clots and dashes as a signal that they possess. The Navy Yard station con- of all nations, despite differences in lan- guage. the station is on the air and free to handle tinues to send out its warning, in case a traffic. ship unaware of the SOS begins to trans- The call "SOS" passed through a process mit. of evolution. The first suggestion for an "SOS" FROM THE ! "TITAN IC who are able international distress call for ships was Broadcast listeners to read Several minor emergencies at 'Sea re- the Morse code and the quick made by the Italian delegates at a prelimi- Continental vealed- that "CQ" did not sutficientl express nary meeting to consider radio telegraphy, flashes of radio abbreviations can often fol- the urgency required for distress purposes. rescue arrangements; the held at Berlin in 1903. The Italians sug- low the for This prompted the Marconi Company to is- sue a General Order "Circular No. 57" on (Continued on page 1160)

Below (louer left), the In the canter. above, is switch which is turned the latest Marconi A uto- at station 14' E A F vatic alarm apparatus when a SOS is re- whieh takes the place of ceived by Me oper- an operator in :.catching ator who keeps con- for SOS signals. Ir se. slant watch. This dis- lect: the distress signal connects the remote. front any other messages control line from the sounds a bell. and. transmitter and broad- Wide World. calling stops, so far l as this station is con- Below (at the lower cerned; though inland right), a view of the stations May continue. operator's ,room on the Herbert Photos. SS. "Southern Cross," showing receiver and tele- graphic transmitting key. ® Herbert Photon.

www.americanradiohistory.com 1110 Radio News for April, 1928 9k Oidhr yrJ*1ip By .1e1-tFancr's l m tigee r. -l're got you logged, and my dials are set. Your program's nice and loud I runs the boat up to the dock and Jerry "Again!" he mutters. on my super-het; and Long -Wave helps me take the stuff back up to his joint. "Nor I exclaims. "Impossible!" Papa, you ain't a-gonna fade on me!" We putters around up there for a coupla "But she did -oh, you're fooling r de- spasms, until the evening papers arrive. dares Jerry, coming out of his daze. ".loe, The Master always allots a certain daily did you ever play the horses, as they say ?" IT'S one of those August afternoons just period for getting the low inside on how I grins. "Prior to annexing Doris I blew made for white duck pants, i. stiff the other half lives, and he flops into his my split -week savings on the Saratoga breeze and a sunburned neck, and I'm old morris chair with a lapful of sheets. Ships, but none of them ever made port out on the Sound in our new speedboat, I'd not have given any thought of it, only In recent years I've been kept in sight too Bow Stealer, practicing the lyrics and learn- I happens to get a slant at one of the much." ing the libretto of My Radio Girl -the on- papers. It's a publication devoted exclu- "What I mean is, do you know the cus- coming season's musical smash, if you be- sively to the art of lasing currency on the tomary methods of betting, and have you lieve the producers. Suddenly the telephone ponies. any acquaintances in the game ?" rings! Jerry plays a scientific hand of bridge- "More than I know what to do with," 1 No, it's not the heat. Besides stcdying he would-and can, when in the mood, he grins, making a wry face. "I wouldn't wish my part I've been helping The Master in astute at poker; also, on certain memorable any of those touts on you, though. Why ?" some minor experiments, and we've a flock occasions, the dice have displayed remark- The Master sits up, and it's plain the old of apparatus aboard, including a small able gathering proclivities while under his dome is working without static. "I never twenty -meter radiophone, with an auxiliary guidance. But he's not essentially a gam- would have learned about this, 'except for transmitter to ring a bell, so s I won't have bler, unless it be for a principle; that he's a casual friend who wrote me from up- to keep the cans on in the sun. I grabs taken up horse racing is a new one on me, state." the instrument and answers Jerry. and I've known him four years. "Yes?" "Go out beyond Buoy 3," he directs, "and "Since when ?" I demands, seizing the "The particular horse involved runs un- turn knob B-14 on Panel 2 until the red in- sheet. "And at your age, too! I thought der the cryptic name of Fuse Plug; it is dicator on Dial 6 registers 18.5." you knew better!" an outlaw, of course, playing only the minor I haven't the least idea what it's all about, The Master smiles faintly. `Only morbid events at small county fairs?' but being wedded I can obey orders; I does curiosity, Joe," he answers. "Curiosity plus "Fuse Plug!" I snorts. "What's his ca- as asked and shortly receives The Master's a mild determination." pacity?" thanks, and the request to come ashore and "To what -beat the game ?" I inquires. "From Harry's description, the animal help somewhere. "Don't tell nie you've worked out a sys- seems to be an old mare and, while origi- Formally, I'm Joe Hammerstein, dancing tem r' nally of racing stock, has been in commer- comedian, and reside with my exit- light, Jerry almost laughs out loud. "I fear cial service on a transfer line until this Doris, and four radio sets, at Brightmere- you've misconstrued my meaning," he re- spring." on -the -Deep, Long Island. We're due to plies. "No, Joe, I'm not gambling. But I nods. "So far so good." begin rehearsals with a musical comedy next the career of one horse is interesting me "But, no," declares The Master. "This week; and, as a novelty, they've given the strangely." horse, Fuse Plug, while only entered in opera a plot, so we've lines to remember. "Other people have been affected the same free- for -all meets, invariably wins first prize Jerry Lawson, alias The Master, s our way," I grins. "Only they had to walk by the simple trick of lagging until the local gift to science; he's twenty -five, tall, home. What's the racket this time ?" final stretch, and then rushing ahead in a slim, dark- haired, a power in Wall Street I hands him the paper, and he hunts final blaze of glory." and an authority on radio. Once, in the through it until he finds the results on a "Common enough," I disparages. "The fall of '09, he was known to make an orgri- certain race, away back in the sticks. His nag can't stand up under a continuous rial wise -crack, wholly by accident; since face sorta tightens, and then relaxes, with grind. They save the steam for the end." then he's basked in its memory and turned an expression of puzzled annoyance cross- "I realize that," mumbles Jerry, again his mind to higher things like aerials. ing his handsome map. perusing the paper. "Yes, here it is-the horse is nine years old, but has never been beaten since the opening of the season." "Framed," I states, laconic. "Those gyp horses run under cheap syndicates, and it's all pre -arranged." The Master shakes his head. "No, Joe, this case is different. Harry saw her race five times, and in each instance Fuse Plug performed as I just told you "Doped, perhaps." "A drug could hardly be regulated to take effect at a given moment," argues Jerry, "and even so, it would be noticed. While the supervision at these small races is not thorough, it would nevertheless be difficult to use a stimulant of that nature without eventually being apprehended." I scratches my dome. "They used to use a battery and a spark coil, to shock the horse," I offers. Jerry arises and paces the floor. "That seems to be eliminated, too. There have "The box in the barn contained a radio receiver tuned to one wavelength and oper- been other inquiries concerning Fuse Plug. ating the main switch to the primary, which gave Fuse Ping the radin whip." Indeed, it is only through her peculiar

www.americanradiohistory.com Radio News for April, 1928 method of running that the racing sheets the fair. Our plans have been made; in or- remains last; then the mare suddenly even list her exploits. Harry tells me that der not to create suspicion, I leaves The whoops into it, passes the others like a authorities, including the S. P. C. A., have Master just outside the town limits, and Parisian taxicab, and crosses the line a gone over the animal, but have been unable walks in as a hick visitor. Unless he needs winner by two lengths! to find any traces of either drugs or other me, in which case he'll signal, I'm to meet Something spurred that horse on, and it artificial means. There is something inordi- him after the rices at this spot. wasn't ambition! nately clever about it all. I should like to According to our arrangements, I'm to Then I quietly collects, so as not to run investigate." watch Fuse Plug run and, if she wins, go too much risk of being identified later. "Hop to it," I says. "Need any help ?" to the management and claim the horse is Somebody might recognize me as having "When do your rehearsals start?" crooked. This is to give me a chance to won; but only the payoff guy was there, This was a Monday. "A week from to- inspect the animal at close range, also the and he was still busy when I put in my morrow," I replies. "Can we catch Fuse jockey and saddle. kick. . Plug somewheres near here by then ?" The Master gets an infield permit -he's I finally gets a chance to examine the Together we goes over the paper and supposed to be a news -reel photographer, nag, with a couple other bozos that says finally locates a dinky county -fair outfit and fusses witha camera for atmosphere - they lost. Nothing wrong with the horse, that's billing Fuse Plug to run for three and drives up to the turn just above the nor with the jockey. The saddle is regu- days. home stretch. Should we pass each other, lation. "Tuesday, Wednesday and Thursday," we're to be strangers. All's lovely. "I guess she's square," I mumbles to the reads Jerry. "Why, that's tomorrow. I've Our horse is entered in the third, with a owner. "Sorry." been through the town -it's only seventy field of nine; one look at her is the cue for I walks to our meeting place and pretty miles upstate. Will you come ?" a big howl. soon The Master rolls along. He hasn't "Delighted," I answers. "Have you any Fuse Plug was a racing filly once, but much to say, but I can see he's learned idea what it's all about ?" she's sorta forgot herself and grown heavy. something, so I stays shut and lets his brain The Master nods vaguely. "I've several At that, though, the beast has pep, and is in function. theories, but I'll have to do some experi- good trim for her age. The next day, Wednesday, Fuse Plug is menting first. We'll drive up in nay lab I mixes with the gang until the track due for a double -header, morning and after- truck events come up. Then I privately places a noon. We're there again, early, and ap- This latter is a small, inconspicuous tar wager on Fuse Plug-just a hunch, and parently separately. with an enclosed body, like a delivery Doris'll never be the .wiser-and edges Just before we reaches my stop, Jerry wagon. The Master uses it on tour, and at through to the rail. confides a few facts. times when he don't want to be bothered by At the start Fuse Plug brings up the "Across the track from where I parked, spectators. The bus is built low, and has a rear, but she holds her own, and in spite of on the outside, is an old barn, abandoned straight -eight motor -there have been times her apparent clumsiness it's plain she once as a part of the fair grounds except for when speed was very, very necessary. knew how to run. Until they rounds the storage. I shall have to explore that im- Early the next morning we drives up to curve where our truck is parked Fuse Plug mediately. In the meantime, you keep your eyes open, and be ready for anything." "O.K.," I replies, saluting. The morning race goes off just like the one the afternoon before. Fuse Plug does (Continued on page 1164)

Re shoes the fat Mayor the saddle. The official grunts. "Battery ?" he demands. The Master shakes his head. "No, strange as it may seem, Fuse Plug was controlled by radio." But strange to say nobody slips Jerry the bird.

www.americanradiohistory.com i>> Radio :News For _ -lprü, 19'A

PAPA WAS NO JACK BARRYMOREI TOO TECHNICAL! NO DOUBT ABOUT IT! Mantua (wife of Miami.: "I just LOUD SPEAKER famous radio an- love to sit with (in its best static j nouncer) : "N e w Jim in a darkened manner): "Bang! run along to bed. room with the Crash! Help! Po- kiddies; and, when radio playing soft lice! Murder!! Cam?,^ q you say your pray- music.." BANG!!!" ers, don't forget to MARJORIE: "Oh, RADIO FAN do as daddy said, I might with some (whose location is °r and pray that tele- boys Freddy -but more pacific): ' I vision will may never keep both "Hooray! I've got come." I'm. G hands busy on the - Chicago ! Mortimer. dials." r -Mrs. Bill Howard. THE CONTROL THAT FAILED NOT A BARK IN A BARRELFUL Frier Housemen): "Is Professor Wise HoQUES: "Say old man, how do you'man- NOT THAT KIND absent-minded ?" age to get such perfect radio reception ?" JOHNNIE: `,`I got Greece on the radio last SECOND Drrro: "Is he? Last night, when JouvES: "I blow New Silver cigarette night!" the baby cried, he twisted its nose to elimi- smoke into my loud speaker, to ease its Marina: "Well, you wipe it off before nate the static." throat " your father sees it!" THE BOOKSHELF. UP -TO-DATE -Leslie Carpenter. LYDIA: "I've often thought how THIS page is devoted to humor of purely ALWAYS FOLLOW INSTRUCTIONS radio interest; and our readers are in- romantic it would vited to contribute pointed and snappy SIIARPE (radio he to he cast away Jokes-no long -winded compositions-of an expert: "What on original nature. For each one of this na- on a desert island." ture accepted and printed, $1.00 will be earth are you Nun*: "W h a t paid. Each must deal with radio in some grinding up ' that of its phases. Actual humorous occur- ten -tube set would rences, preferably in broadcasting, will be copper wire for ?" you with preferred. Address Broadcastatics, care take RADIO NEWS, 230 Fifth Avenue, New Duxii (radio you ?" York City. novice): "W e II, rOSITIVELY THE LATEST I'm putting in my VAN: "He's the last word in radio an- radio set and nouncers." HOW HE REMEMBERED RADIO News says a ACQUAINTANCE: you live in Pifer; : "Yes, he's the guy who signs cff CHANCE "So good ground wire the station every night r' Woltville, eh? Didn't you have a terrible is the most important thing about the in- -Win. G. Mortimer. storm down there last summer ?" stallation." -Paul Harrey. RADIO FAN: "We sure did. That was the SPEECHES GO ON FOREVER night my aerial blew down. "" SOLVING FTRST WEARIED THE MYSTERY Vona: "What did NOR THE AUDIENCE (LUCKILY) Docroa: "You're you think of Sena- F I R S T MICRO- color.: blind, m y tor McBuncombe's PHONE : "A good good man r speech over mike is a broad- JONES: "Ah! I WAAK last caster's best het that's why I night ?" friend." always get t he SECOND W. V.: SECOND MICRO- Blue Chain pro- "I think they ought PHONE: "Yes, i t gram when I try to have given him will never tell him to tune in the a shorter rave - when he has hali- Red r - 1Vrn. G. length." - tosis." Mortimer.

RADIO RHYMES No. 6

_/ 'YOUNG MAN! -- 1 WOOLD 1 CRAVE TO HEAR ONE WELL ,51R ! PERMIT ME YOU TUNE ONE V010E. DESIRE TO GET SINGLE SONG -- HEGE TO 514 W fQOM A DUET -- YOOR VERY BEST SE LECTIUE P D NOT A mercLEY A REAL SELECTIVE ANO HEAR A SOLO Ord 5E ! - SCRAMBLED ?Heon1Q!. RADIO! Tins 5er!

www.americanradiohistory.com Radio News for April, 1928 Dr. de Forest Talks on Radio

Forecasts of the Near and the Distant Futures of Broadcast- ing, Television, Radio Apparatus and Radio Entertainment

V the "Home Science University" series I am sure that great strides will he Made of Station Wit NY, broadcast on Janu- in the matter of improved quality of re- ary 11, 1928, 1)r. Lee de Forest was production. 'l'he better type of console interrogated by the Editor Of RADIO radio with built -in loud, speakers, particu- Nsws on a nuniher of radio subjects. The larly the higher- priced ones with phono- entire interview is published, verbatim. graph combined, will be more and more in as NIR. GRRNSRACK: -.111e quest ionS which I demand. And prosperity becomes more widely distributed, and particularly as the 0111 going to ask you tonight, Doctor de Forest, are put to you in such a Yvan' as educative influence of radio, above men- perhaps the man in the street would put tioned, works its indirect benefits, more them to you, if he had the opportunity or, and more will discard their cheap "noise - may I say, the good fortune to speak to boxes" in favor of more expensive and you. I shall try and make the questions properly -designed amplifiers and Ioud- as simple as possible; tweause you appr(- speaken s. Muclt progress will be made in eiate that, perhaps, not all of our listeners 1928 in the field of broadcasting with short are technically inclined, and few can know wavelengths below 50 ureters; but it will all the technicalities. 'l'he first question is: 1:d:e more than one year to iron out sue - eessfulh the intricate difficulties involved "iI1iat (h) you consider the greatest step in building reliable ie1'eirers for operating in radio progress for the year 1927?" on such short waves. It will be a long and I)R. DE FoltEST: -\ir. G('rnsback, before slow process of infiltration that short -wave I answer that and the following questions, Ino:ukasting must undergo before it can I want to say to the radio audience, that invade, to any large degree, the popularity my remarks tonight will not be to tech - which the present range of broadcasting pical. From the tenor of the questions channels now enjoys. 'Itich are being proposed to toe, i art talk - MR. GHRxsuiACK: de Forest, you ing on strictly radio technical matters; butt -1)r. probably read a few (lays ago, that IIarry I trust that I will use language that those 1.111Ider said he would never broadcast. really interested in radio will understand. Ile said the present reception is not at all what Now in answer to your first question. I should be. don't whether you consider that the most important radio de- Dr. Lee de Forest it I know read that in the newspapers. That brings velopments in 19.27 route under the beads he quest of the rapid elimination of ".'" and "II" ion: batteries for radio receiving sets, and the "Wherein does the present -tall radio set meat of the public's taste for good music. progress in the development of short -waye- fail, if it (loe..s fail? Countless thousands are now educated to length broadcasting. (Treat progress has Da. uK Foursr: had not read that ar- Mott for and genuinely appreciate a type -I also been made during the past year in the ticle; but it exactly lits with a statement of music of which five viers ago they were simplification and standardization of timing made to me at luncheon today- with a friend entirely igflnr ;i lt, or under no conceivable devices; so touch so that, for all local work, who condition would trouble tlmuis'Ives to hear. recently met ten of the Players at the the single -dial control, even though this Players Club. l-le said he talked with them This cultural influence of radio is cumu- may operate three or four condensers, gives about radio, and he found that only one of lative, accelerative. I have no doubt that, fine selectivity and adequate volume. 'l'hr the ten owned a radio set; rive years from now, most of the ('ileap fire of the ten 1)X fan still v, ants individual -stage con- had owned radio sets but, with their cars jazz, and Mediocre music which the public trol with vernier condensers; but the great so well trained to fine enunciation line now enjoys will he as distasteful in the and mass of radio listeners, tIio now over- music, they discarded the sets; and the United States as it has always been among whelmingly preponderate in and around our the More cultured and umtsie- loving peoples other four were not interested in radio. larger cities, are rapidly becoming educated of Europe. Many present -clay radio -sets are deficient the that can ob- to fact the very liest they in the quality of their audio amplifiers and tain of radio anywhere comes front nearby GER\SISACK: -That probably answers particularly in the loud speakers employed. stations. Therefore the extreme accuracy the next question, wltidt i shall put to you 'l'he radio -frequency and detector systems in tuning each individual IL.B. amplification anyhow. have a high state of stage, in order to pick up with maximum lu rchat directions do you Mink present attained refinement, volume long -distance stations, no longer broadcasting shoald or can gn.' What are but too little attention has been paid up appeals as it did. your views? to date to the audio -frequency -amplifier end of the receiver. 'l'oo little iron is used in MR. GKRxSn.(CK:- Thank you, Doctor. DR. DE Foiwsr:-'l'Irtt calls for a some- Another question: what More technical answer. As to the most of the transformers; too few ampli- fiers employ push -pull circuits; and there What are your views on the present technical developments awaiting us in 1928, broadcast art: is too little inclination to employ expensive power tubes in the last stages; with the l)R. Dr: Font is it source of im- :r: --it result that ive frequently have distortion measurable gratification to me to observe due to saturation in the transformers, or the very marked increase in the quality of :CO.*? re- overloaded tithes somewhere along the line. musical progr,uns now being broadcast, as The accompanying lecture "h'.l'P, compared with that of two years, or even eenNy given over S'lation lI Ma. Gsnxsn. cK:- -That partly answers my .\-ere Yo1,, Us regular wed - 1)111' year ago. This is particularly notier- during next question, which I will put to you if ''The Home able on Sundays; a lover of good music may uesd(n/ evening feature, you have something more to say about it, then listen to his radio for hours at it titi e Science University." and that is: During this Itour, :cell-knot-cm per- and hear nothing iuit inusic of the highest is lacking to make present clay sets sonages in. the arts and sciences lec- inat order. Today's radio is abundantly making more perfect? good my prediction of many years ago, ture at II-RAW and Mr. Hugo (7erns- con- DR. m: FoRr.Sr: think the greatest need that radio would be instrumental, as no back, Editor of this publication, -I audio- frequency other institution of man's creation possibly ducts an open fortin,. in that direction is better could be instrumental, in a rapid develop- '(Continued ón page 1177)

www.americanradiohistory.com 1114 Radio News for April, 192e

A broadcast station capable of transmitting with a power of 120 kilowatts was opened recently at Zeesen, about 20 miles south of Berlin, Germany. la the illustration below is 'shown the lower end of one of the aerial towers, and the heavy weight used for maintaining a fixed tension in the wires. ©1'. & A.

E Lif1111J1Itl/A1tl(tJtltfl/llllltlilUllllllllll1l= li A problem which recently has been solved is that of com- municating from any point with an airplane by means of Mc portable transmitter shown in the above illustration. It has a power rating of 50 watts and can be used for tither telegraphy or telephony. Underwood & Underwood.

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In the illustration above is one of the two 210 -meter masts sup- porting the transmitting aerial at One of the main troubles ex- duc Zecscn broadcast station; it perienced when coinmu uicatiug is designed for a 100 -tot strain. between as airplane and the The wavelength of the station, grou od. or between two airplanes which supplants that at Koerig- in flight, is that an operator in -mst:rhausen, is 1,250 meters. the airplane lias trouble in hear- Notice the modernistic trend of ing the radio signals in the the style of architecture in the phones, because of the motor station building. noises. in the illustration above © P. & A. Photo. is simian a new helmet, designed for aviators, in while the phones arc an integral part of the head coven,,,,. The microphone is In the illustration at the left is especially constructed and is the novel horizontal control board strapped to the operator's chest. of the Zeesen station; all the © Underwood & Underwood. ! R3 + ft operations are controlled from t c -e this central point. O Underwood & Underwood. E` Co' M7tiJ1JUUpl ni Ì7 n

www.americanradiohistory.com Radio Ncws for April, 1928 1115

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Listening to a radio program in the Robert Morris Hotel, Philadelphia, in which every guest has a choice of three different radio programs.

E 1 ¡loto the headphones are hung over the outlet panel which contains the three lacks supplying the three optional Indio programs.

bbit 7 cup Ill /!nogg!! III IIIIIl /lllf if /utI1lII llftr Three antrn.ias arc available for ;hive receivers in the Robert .17rrir Flotcl; tite four;le set is for emergency ;se. Special amphilers are used :o that eery guest has clear reel! pfist, available at ro7d headphone volume.

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Above. the radio inste!latitr, in the Hotel Georg. (lash ington, Iac.a?uvillr. Floida. In every guestst roa r: and flu roughout the lobbies, a niug rooms, etc., are loto-' speakers which bring to the guests the best radio pro grams of the day. In rase special announcements o- emefprncy requests have to 'e made, the mataguntea_ can get in taurh with every guest within a very fe., seconds. The relic, eçgipnrut shown above can b. used for either reception of programs or general air - nounnun, by the throwing of two or three switches At the right, ute of the r.aoms, showing the loud- speaker equipment which is provided for the naves who te,sh entertainment 'rouaM to tugs:.

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www.americanradiohistory.com 1116 Radio News for April, 1928

The Radio School Teacher is Here Further Opportunities for the Custom Radio Builder, in the Equipping of Schools With Receivers, are Explained

By Armstrong Perry

A\ATíO\AL system is being devel- necticut State Board of Education conducts oped for broadcasting short, super- the courses; Station WTIC gives its serv- have often pointed cc lative radio programs intended es- T,jJli oat that ices. The Connecticut State College of Agri- ( local cleat of money be pecially for schools. Already, in rr crut made culture was hooked up with t TIC in broad- by custom radio builders, through equip- Connecticut, a course in music appreciation the lessons, as long as money was ping of schools casting has been conducted for a year and courses with special radio sets available to pay for the telephone line that for educational Purposes. As Mr. in trees, geography, children's hooks, birds, connected it with the studio. animals, insects and flowers are now being Perry shows in this article, there is a Announcements of the course are broad- bill market for radio sets to broadcast. 'l'hcy are received in schools which up cast at the beginning of the year, and are throughout this and other states. this time, has not been exploited; and sent in printed forni to the officials and great possibilities A group of philanthropists is at work on are in it. teachers of the schools throughout the state. Though it is, of course, possible a plan to offer free of charge to every school (and There were only half a dozen radio receiv- in many cases desirable) for schools to in the United States, the services of pre- ers in the schools when the first announce- purchase -built sets, it is eminent teachers to assist in the work of factory true ment was made; but, before ninny lessons also that, even when such sets are eased, the faithful resident teachers. For good were broadcast, it was found that 60 schools power amplification becomes necessary measure, it plans to add music and talks had purchased :35 were and, for best results, a number of loud receivers, renting by outstanding national lenders, then and theist and I62 were sending pupils to private speakers should be stationed at different women who are making history. Leading hones, where they were invited to listen in. points in the school. Here is where the educators are cooperating in the movement. One radio dealer installed a custon, radio builder can do a worth- enterprising such prospects in view, and with in school each With while lob. receiver the in his town, day radio receivers available everywhere, it is when there was a radio lesson, and connected In larger schools, it will be desirable no wonder that schools are hurrying to in- it with loud speakers in seven class rooms. to build a special set for local require- stall equipment. One located in Brooklyn He says that it has proved good advertis- ments; particularly where one such set is estimates for installing a ing. Forty -five superintendents of schools considering supplies different classrooms, each of master receiver with eighty loud speakers report that pupils in 75 out of the 169 which has a loud speaker. It would in the classrooms. towns under their supervision have received seem that here is one of the best mar- the instruction. 'l'he officials re- kets for the custom radio builder at at WTIC CREATING A MARKET port that 275,000 pupils in five states heard the Present time. -EDITOR. The experience in Connecticut shows how one lesson in which the Travelers Symphonic radio programs help the schools. The Con- Ensemble provided the music. Has any

www.americanradiohistory.com Radio Nees for April, 1928 1117

The corers of four Gooks prepared by school children, in which Were curil tutu their impressions of the musical coe rse broadcast by radio.

171I:rr new school method ever made such a nature study. 'liar course led the pupils to in also. A new bond was created between gain in its first year? more serious reading, for they wanted to the school and the home. know more about the men who had expressed ARE PUPILS ENTHUSIASTIC their thoughts and feelings so beautifully in USE OF RADIO BY EDUCATORS INCREASING Educators are inclined to conservatism music. Drawing improved when the note The selection of the course in music appre- and many of them prefer to follow \yell - hook covers and illustrations were under ciation, as the first to be offered to the beaten paths, but pupils are eager for new way. Even arithmetic became more inter- Connecticut schools, was made after care- experiences and adventures. 'Wherever a esting, because the music was written in ful study. England has a broad curriculum progressive Icachlr grasped the possibilities three -four. four -four and other times and of formal courses of instruction broadcast of the course and placed it before a class the wily of it had to be figured nut. on a national basis. Atlanta, Oakland and with reasonable preparation and enthusiasm, l'h( (nurse increased the use of the phono- Denver have provided regular courses by it was appreciated. In Pomfret, Connecti- graph: for, after hearing a musical com- radio for several years. Music has been cut, for example, they could hardly wait for position rendered and explained by the found the best subject to start with. the next. program; Pomfret has always been radio teacher, it was a delight to hear it 'l'he Connecticut State Board of Educa- progressive and adventurous, Peer since the again and again on the phonograph in order tion provided its schools with printed syl- day )vhen israel Putnam pulled the wolf to catch every phrase and expression. labi in advance, which gave the educators oil of the cave in that historic town. 'l'he utmost popular lessons were those in an opportunity to plan their work. Printed The of one school asked if they which pupils took part. Glee clubs, hands programs were distributed, one for each might make booklets about the radio music and orchestras from city high schools were room in each school, on requisition of the ceuurse; permission was given and it became heard sometimes in the course. More of superintendents. 'l'hat gave each lesson the an absorbing game. They vied with each them were beard after that through the enjoyable aspect of a convert other to produce the most attractive designs radio sets at home. It was a great incent- I)r. N. Searle Light, director of the divi- for the covers; they wrote accounts of the ive for pupils to learn to plat and sing sion of rural education, has been placed in music that they heard and told about the and try to improve, so that they might some charge of the courses, because the need for lives of the eouuposcrs; they illustrated the day become radio artists instead of mere them seems even greater in the country pages with original drawings or with pie - listeners. than in the city. Iie reports that the first lures clipped from newspapers and maga- Classical music, which often bores the year's experience justifles the continuance zines. They prepared and bound the pages children of this age of ,jazz, came to be un- and development of instruction by raidio. will' the greatest care. One little girl re- derstood, appreciated, longed for. 'l'he :Martin B. Robertson, state supervising wrote one of her pages four times before (course deyelnpe(I a demand for lectures, but agent, says that the course developed appre- it Caine up to her ideal. that came from teachers -the pupils were ciation of the best in music, gave an oppor- almost unanimous in requesting "more music, tunity for the growth of an attitude of MUSIC COURSE INCREASED INTERESTl{EST less talk!" Some, however, said: " \Ve like careful listening, and enriched material for 'l'he teachers were serpnised by unex- programs that are like regular lessons." (Continued on pate 1165) peeted developments; tluy IIrnisclycs began The effect of the course was not confined to appreciate music its they never liad (lone to the school room. Pupils went home to before. Pupils renewed their interest in tell their parents about the new teacher who class -room work, because the music and the talked to them from way over in IIartford, filets concerning it were closely related to and found that mother- had been listening other studies. 'l'hcy learned to tell the stories of \íacDmvell's "Of a Tailor and a hear," Nevins '°l'he Rosary," and other songs. That led to development in oral com- position. The note books made written com- PoSttio more interesting. Penmanship im- proved as each pupil tried to make his hook Me best. 'Hwy learned to spell time common words used in amide; those which they mis- spelled were likely to appear in the next day's spelling lesson! The social studies, history, geography and (ivies, took on new meaning; bc(arusc the homes of many of the eonapnsers were in places found on the mops and tapir lives were associated with the history of the United States and many other countries. "Time Ballet of the Flowers," "lime Pussy Custom radio builders should carefully con- sider Willow Song," "Raindrops," "The Trout," the hoards of education as a potn Hal radio market. and "The Mouse Trap" connected up with

www.americanradiohistory.com Ills Radio News for April, 1928 cl 111!l'I,i'n",,, Names and addresses of manufacturers of devices described in 0 k' .,. -t this departmentp mayY be obtained byY writingg to the "I Want to rli - Know" department of RADIO NEWS

Simple Device Provides "A" resistance units, a multi -point switch, n New voltmeter and a circuit- breaker. The re- Socket -Power Unit For Power For Farmers sistors (R)' are connected in series and re- Sets Using 199 -Type Tubes duce to a suitable amount the voltage ap- WTHEN designing accessories for radio IIE "A' power milt illustrated on receivers, a large percentage of the I this page was designed especially for manufacturers in this country have con- use in the battery compartment of a popu- sidered only the demands of the broadcast lar superheterodyne receiver, which uses listeners who reside in the cities and towns, tubes of the 199 type; but it may be em- and have ignored almost entirely the needs ployed to advantage for electrifying any of the farmers, who wish also to enjoy radio receiver using 4 -volt dry- cell -type tubes. programs. In more than nine cases out of A large majority of the receivers using ten the socket-power units, chargers, auto- 199 -type tubes obtain their filament power matic relays, benefit etc., designed for the from three No. 6 dry -cell batteries con- of the city user are of no value to the nected in series; and these batteries are fa river whose house is not supplied with usually located in the receiver cabinet. electricity from the city power stations. Therefore, an "A" power unit for sets of In a large number of modern farm and this type should be small in size, in order rural houses is electric power obtained from that it may fit in the space formerly occu- a 32 -volt farm- lighting plant; this consists pied by the batteries. The "A" power unit of storage a bank of batteries, which are under discussion answers this requirement. is housed in a metal case 4 by 9 inches General view of farm "A" power unit housed It in a compact metal case. The knob, VR, ad- by 6 inches high and weighs only 111/. justs the filament voltage; the voltmeter VM, pounds. It will provide pure direct cur- shows the potential at the output binding posts (el); and the knob B may be used to prevent rent of 0.6 amperes at 4 volts, which is the .hunt tirenit- breaker from operating. ample for the operation of any receiver using 10 tubes or fewer. plied to the filament. 'l'he switch (VR) There are on the power unit no knobs connects various portions of the resistance or dials which require adjustment. Two SHUNT RELAY(CB)OPENS bank into the circuit and in this way ad- CIRCUIT WHEN OUTPUT the POTENTIAL REACHES 6.5V. justs output voltage to the required value. The voltmeter (VM) registers ac- curately the exact voltage at all times; and the circuit -breaker (CB) prevents Complete schematic diagram of "A" power unit the pos- which operates from a 32-volt D.C. source. R, sibility of applying accidentally an exces- resistance bark; VI?, voltage- regulator: CB, sively high voltage to the tubes, as it is so circuit-breaker; 1'31. voltmeter. adjusted that it opens the circuit when the potential difference is over 61/, volts be- charged each day with current from a small tween the output terminals. electric generator driven by a gasoline The entire device is housed in a compact motor. Such an outfit provides an ideal metal case which Measures 5x 73/e x 914 source of filament power for a radio re- inches. The voltage-control knob (VR) ceiver, and recently a manufacturer has and the voltmeter (VM) are mounted on placed on the market an "A" current- supply the top. The plug (P) is connected into unit which, when connected to a 32 -volt the 32 -volt supply circuit, and the binding D.C. supply, reduces the voltage to the 6 posts (A) provide the 6-volt supply to the required for operating the average set. The receiver. B is an adjustment knob which unit will be found pictured on this page. may be used to prevent the circuit -breaker The schematic wiring diagram which ac- from operating. The view with the cover This compact unit "ray be used to provide (da- companies this article shows that the "A" removed shows ment power for sets using up to ten 199 -13-pc' the location of parts inside retching tubes. It supplies O.6 amperes at 4 current- supply unit is of very simple de- the unit; the series resistors are located un- volts D.C. sign. Essentially it consists of a bank of der the sub -base. binding posts are provided, for connecting wires to the battery posts of the set, and there is a filler hole where distilled water is added at rare intervals; in addition, there is the wire and plug which connects with the lamp socket. To install the unit it is The arrangement of ap- necessary only to connect two wires to the paratus inside the "A" posts and insert the plug in the socket. supply Unit i.,- clearly shown at the left. The After it has been installed it is necessary resistance bank is located to add water to the filler hole on an under the sub -base and aver- the heavy sires run from age of only once every six months. It the contact points of the should also be remembered the voltage -regulator to vari- that unit ous points in the resis- is turned on and off at the lamp socket tance unit. and not by the filament switch on the panel of the receiving set. Electrically, the unit consists of a step - down transformer, a rectifier of the elec- trolytic type, and a filter system consist- ing of a heavy -duty choke coil and a high-

www.americanradiohistory.com Radio News for April, 1928 1119 capacity electrolytic condenser bank. Power storage battery, of the type used for radio units of this type, which were designed to purposes, is charged at a rate of approxi- supply filament current to receivers using mately 0.3 amperes. 8-volt tubes, have been described previously The construction of the unit is very in this department. Those who are inter- simple. It consists of a fixed resistor and ested in a more technical explanation of an ammeter, connected in series with the the action of the electrolytic rectifier and battery and 110 -volt D.C. line. The ammeter eondenser bank should refer to articles is of the "charge-off-discharge" type and which were published in the December 1927 is used to indicate whether the charger is and February 1928 issues of RADIO NEWS. correctly connected. 'l'he resistor is wire - Although the devices described in these wound, vitreous -enameled and will not burn articles are different in external appearance out when operated under the conditions de- as it larger in size, they operate on identical scribed above. The unit is enclosed in a electrical principles and are of similar fì 1 nunpaet h irk /r ri;,; r,t, r 1:11i1 for operation in cylindrical metal ease, inches long and 21/I con.st suet ion. 110-vo11 U.C. circuts. inches in diameter, which stands oui legs one IL sheep be explained that this unit floes inch high. not supersede all batteries. It provides there is a demand for such a device. There are several precautions, which must shows a filament power for 4-volt tubes and re- The accompanying illustration be taken in connection with operating direct - trickle charg- places the "A" battery; but "B" batteries simple, efficient direct -current current trickle chargers. As one of the to charge storage ":1" or or n "B" power unit cire still required. It er. It may be used matins carrying direct current is connected a I10- 1.25 -volt should also lie pointed out that the unit "13" batteries direct from to the ground, it is necessary to place in nay be operated only with 110 -volt, 60- direct- current line. It will charge from one series with the ground lead of the radio set at one time and cvcic house current. to forty lead -battery cells a condenser between .002- and 0.5 -mf. is between 0.1 and 0.3 the rate of charge capacity, to prevent a short circuit of the upon the number of cells amperes, depending 110 -volt line. It is wise, also, to connect a 6 -volt New Trickle Charger For Use in the series connection. .\ standard similar condenser in the antenna circuit, If D. C. "13" batteries are used for the operation of In Circuits the receiver, the trickle charger may be many different types of trickle chargers connected as illustrated in the diagram. have been developed for operation from 11(1 - I however, if the receiver is operated with a volt. alternating -current house-lighting ein- "I r socket -power unit, it is necessary to cuits, and these units have become very disconnect the trickle charger from the popular among set Owners who wish to house -current supply, by means of a double - electrify their receivers at a low cost. how- prole switch, when the set is being used. ever, few trickle chargers have been de- When connecting the charger with the signed for use in direct- current circuits. As .002mf. house current for the first time, it is im- the publie utilities, in a number of the large portant to make sure that the plug is in- cities in this country, including N yv York J)iagraaa shores method of connecting triclle serted in the light socket in sudi a way that clanger (,lI) a Pity, furnish homes with direct current, fo radio .cet when batteries mye used far the '!t" ,mont. (eon/Mucci On paye 1183) $100.00 monthly Prize for Set Builders

eon,junethai with the change of policy 1:1),H1 you to sin' flta uuodcl to New York uhtained the consent of It.uno News. Kindly I editorially announced in this issue, for test. read the following conditions carefully nand Ravto NKW's, during 1928, will offer a In any event, RADIO News reserves for you will see what is wanted: monthly pries of 100.110 to radio construct- itself the right, when accepting the article, set custom builders ors, builders and radio to substitute and specify other apparatus, CONDITIONS AND ItrLES OF THE iMONTIILY for the hest practicable raclin circuit or con- leaving the selection to the editors, if suds RADIO NEWS BUILDERS' COMPETITION structional development of the mouth. should be advisable; but the main features The idea of this prize is to cnconrage of the design as recommended by the con- 1. RADto NEWS desires all new or novel cir- constructors in building. 'l'hc prize is not structor will always remain intact. cuits, power packs, amplifier combinations, tele- given .lyre all radio sels or hook -ups, or All radio mauutfacturers are excluded ision sets, etc. 2. No one shall be eligible for a prize unless all power packs and other constructional trout the contest, as is designed only for it some experimental work, showing the practicability articles, that aaIT accepted for publication. the encouragement of constructors and of the device, has been demonstrated by the builder. Prizes will ttnl' be given on those published radio builders. 3. Photographs evidencing proof of the above in our su -call col "Illucpriuit Articles," where In the past, RADIO News has been re- must be sent with the article first to lieotn NEWS. the article is accepted, RADIO NEWS will either full constructional details are given. sponsible for the Of many If publication im- send for the device, paying transportation therefor, If you have experimented with a new portant circuits; just to mention a few, or build the device in its own laboratory, in its eireuit -if you have uncle an important im- the I'itradyne, the 'Propadyne, the Interflex discretion, provement on as known eircuit -if you have Series, the Strobod'nc, the I'cridync and 4. l'arts used ntay either be standard parts obtainable on the market, or they may be home- designed a new power pack -and providing many others. I1.tulo News desires the best made. 'l'he designer must submit a complete wir- the material is acceptable, 1tAnio News will and latest, and is willing to pay for it. ing diagram, drawn in ink on white paper, also lmblish the article and pay 1100.00 for the Furthermore, in many instances, the sketches showing the outstanding features of the hest one submitted. litiillcr has made capital from his circuit. device in general. Articles giving complete con- structional and detailed information to be sent at be It should understood, that we are not In a rectnt circuit published in li,uno News the same time. interested in mere circuits or mere ideas. (the Super- Hiludync) the inventor, \Ir. 5. Bundle all papers firmly together so they If you wish to cuter into the monthly con- Icwcll, was paid a very large suns for his cannot be separated, and note that on each sheet test. it is necessary that you must give saute novel circuit. It was first published ex- and photograph, entrant's name and address must be clearly printed- No penciled matter considered, ocidence that you have actually built and NEWS. clusively in RAmo l Tse typewriter or pen and ink. Rolled manu- tested the new feature. It is necessary Furthermore, as an added incentive to scripts are excluded from the contest. Use wher- that, with your first letter, photographs the constructor, providing also the circuit ever possible, photo -mailers which are obtainable at stationery stores. should he submitted, showing what work has is patentable, ltnmo News hereby agrees to all 6. The monthly competition closes on the fif- been performed. the editors are suffi- a If take out patent in the inventor's name, teenth of every month. From the contest arc ciently impressed with the novelty of the paying the entire patent fees; and when a excluded ell radio manufacturers, as well as the idea, they will do in their discretion one of patent is issued, it will, of course, belong employees of the Experimenter Publishing Com- and their families. two things: RAmo NEWS will either build to the inventor in whose name it is taken pany entries to Editor. fnnthly Construc- the circuit or power pack, whichever nut. 1)o Address all it not, under any circumstances, send tion Feature, c/o RADIO NEWS, 230 Fifth Avenue, may lie, in its own laboratories, or will call sets to RADIO NEWS without havint+ firs: New York City.

www.americanradiohistory.com 11_U Radio News for April, 1928 When Radio Turns Street Lamplighter

By S. R. Winters

\PERIMENTALLY, a scientist in muting the transmitter only 15 seconds each Washington, D. C., has opened the day. With five seconds' operation of the floor of his automobile garage by radio transmitter, the street lamps are weans of radio. On a railway train lighted; when the operator twists the `off" in France the stations are announced by button in the power house the radio trans- the use of electromagnetic waves. Various mitting set operates automatically for ten critics are employing broadcasting and re- seconds and the lights are s' ltaneously ceiving equipment in issuing orders to their cut off. The feeder or electric -power lines police forces. Hundreds of radio fans are extend to five different sections of Glens using their receiving sets in conjunction with Falls and, although each section or unit is clocks as alarm systems to wake their fami- independent of the other, the entire town's lies in the mornings. An automobile traf- thousand street lamps are controlled by fic count has been made by virtue of radio virtue of the carrier- current system. apparatus. And, now, the street lights of This wired radio system involves the use One of the automatic receivers which governs a lighting district is contained in the box on an entire town are turned on and off in the powerhouse of a small panel board the pole. through the magic of the wonderful radio holding all of the radio transmitting equip- waves. ment; the latter consists of two 50 -watt tential in the feeder wires to the desired A vacuum-tube transmitting set, using a vacuum tubes and a simple oscillator cir- lighting voltage- 110 -and the street lamps small amount of power and operating on a cuit. This panel board contains the electric are then lighted. At daybreak the operator wavelength of 7,500 meters, and five receiv- switches or buttons which are designated as at the powerhouse turns the `off" button ing sets responding to only one wavelength, "off" and "on," respectively. Turning the on the radio- transmitter panel and the ra- control the street- lighting system of Glens "on" button places the radio transmitter dio waves -in this case "wired wireless" - Falls, New York. Street lamplighters in in the circuit for five seconds. The result: again pass over the feeder wires; they are that town, like a buggy -whip socket on an radio-frequency impulses are generated, picked up by the radio receiving sets and automobile, are now out of date. A low - these being fed to five wires leading to as the relays, and, at the proper instant, the powered tube transmitter, not very dis- many receiving stations, where radio appa- street lights are turned off. similar to the transmitting sets that bring ratus is installed. Each of the receiving sets employed in

1777.`ll

i At i n' t-1

music and speech to our homes, feeds a car- rier- current or radio- frequency wave along Above, the lint -tuning units and coupling wires leading to the receiving stations. condensers which feed tire carrier r :n'- rent into the power lines. Right, the There radio receivers tuned to that single panel of the automatic transmitter which wavelength, or frequency, respond to the controls the lighting system of Glens radio wave and, in turn, electric switches Falls, N. Y. are tripped, relays operated, and street this radio-operated street system lamps lighted. NIGHT AND MORNING WORK -lighting contains one vacuum tube, relays, trans- QUICK WORK The five receiving sets, one in each of formers, and other necessary units for the the five sections of the town's street -lighting reception of radio impulses and for actu- This radio system does not disperse waves system, control the relay circuits to coin - ating the control circuit. The tube used in all directions, but concentrates its force plete the lighting -current supply. Trans- in each receiver is operated below its rat- along the electric -power wires and thereby formers in each of the five independent units ing and has an anticipated life of twelve a whole town can be illuminated by oper- of the lighting system step clown the po- (Continued on page 1161)

www.americanradiohistory.com Radio News for April, 1928 1121 List of Broadcast Stations in the United States

Radio Radio s«o Radio Radio er la Call BROADCAST STA. é Call BROADCAST STA. 3% Call BROADCAST STA. c" -w Call BROADCAST STA. 1;4 WI Location 3 li3 Letter Location Letter Location Letter Location 3E 63

KD KA East Pittsburgh, Pa.." "310 50000 KGEW Fort Morgan, Colo 219 "100 KWK 8t. Louis. Mo 234 "10110 WDBO Orlando, Fl t 2.58 500 (Also 02.5. 42.95. and 27 meters and other KGEY Weaver. Colo 201 250 K W KC Kansas City, Mo 222 100 (4Xíì, variable, 250 watts) short -wave transmissions on varying KG EZ Kalispell. Montana... 294 100 K W KH Shreveport. La 395 1000 WDEL Wilmington, Del 297 100 power.) KGFB Iowa City, Iowa 224 10 K W LC Decorah, Iowa 248 50 WDGY Minneapolis, Minn 275 500 KDLR Devils Lake. N. 1) 231 15 KG FF Alva. Oklahoma 205 KWSC Pullman, \Cash '495 500 WDOD Chattanooga, Tenn 244 500 KD YL Salt Lake City. Utah 2'14 500 KG FG Oklahoma City, Okla 216 50 KWTC Santa Ana, Calif 222 100 WDRC New Haven, Conn 283 500 KELW Burbank. Call( 220 >51X) KGFH La Crescents, Calif 224 250 K WUC LeMars. Iowa (day).." "244 150(1 W D W F- W LS I, New Bedford, KEX Portland. Ore 240 2500 KGF I San Angelo, Texas 220 15 K W W G Brownsville, 'Texas 278 516 :lass 261 250 KFAB Lincoln, Neb 319 5000 KGFJ Los Angeles. Calif 213 100 KXA Seattle, Wash 349 500 WDZ 'Tuscola. Ill. (daytime) 278 100 KFAD Phoenix. Ariz 273 500 KGFK Ilallock, Minn 24 50 KXL Portland, Ore 220 50 WEAF tllellmore. N. Y 492 50,000 KFAU Boise. Idaho 285 200() KG FL Raton, N \I 222 KXRO Aberdeen, Wash 227 50 WEAM North Plainfield, N. J 263 250 KFBB havre. Most 275 100 KG FN Arleta, No. Dak...... 200 L KYA San Franelseo, Calif 309 500 WEAN Providence, R. I. 75 500 KFBC San Diego, Calif 248 100 KG FO les Angels. Cnl.(iort.) 204 100 KYW Chicago. Ill 5" 6 "2500 WEAO Columbus, Ohio 283 750 (Also 65.18 meters) KGFW Ravenna. Neb...... '97 1(1 KZM Oakland. Calif 2.111 101) (Also 54.02 meters. 250 watts) KFBI (airplane) Calif 204 50 KGFX Pie rre. S. D. (day)... 254 200 NAA Arlington, Virginia... 4:3.4 1001) WEAR Cleveland. Ohio 400 1000 KFBK Sacramento, Calif 535 100 KGGF Melds:, Okla 207 100 W 6 A D Cincinnati, O 268 WEBC Superior. Nis 242 "250 KFBL Everett, Wash 224 50 KGGH Cedar Grove. La 213 50 WAAF Chicago, III. (portable) 389 50(1 WEBE Cambridge, Ohio 248 10 KFBU Laramie, Wyo. 48.1 500 KGGM Inglewood. Calit(port ) 204 100 WAAM Newark. N..1 ... 268 250 WEBH Chicago, Ill '366 "501) KFCB Phoenix, Aria 244 125 (6XA I. 66.04 meters; 50 watts) (Also 65.18 meters, 50 watts) WEBJ New York, N. Y....."256 501) KFCR Sana Barbara, Calif 211 50 KG HB Honolulu. Hawaii 227 250 WAAT Jersey City, N. J..... 246 310 WEBQ Harrisburg, Ill 224 15 KFDM Beaumont. 'Texas 484 500 KG HC Slayton, Minn 210 WA AW 01111,115. Neb. (dayt inle)441 510 WEBR Buffalo, N. Y 242 201) KFDX Shreveport, La 236 250 KG HF Pueblo, Colo 210 250 WABC Richmond 11111, N. Y.. 309 2500 WEB W Beloit, Wis.... 258 5011 KFDY Brookings. S. 1) 545 500 KG HP Hardin. Mont 263 50 (Also 64.1) meters, 500 watts) WEDC Chicago. Ill 242 500 KFDZ Minneaolis. Minn 216 10 KGO Oakland. Calif '3X4 5000 WA BF Pringleboro, l'a ...... 205 250 WEEI Boston. Mass 508 500 KFEC Portland, ore 214 50 (Short -wave transmitter, In to 40 WABI Bangor, Me. (Sundays) 389 100 (Fias short -wave lmnsnnitter) KFEL Denver, Colo 248 2511 meters. 10.000 watts) WABO See WHEC WEHS Evanston, Ill 216 100 KFEQ St. Joseph, Mo 231 1000 KGRC San Antonio, Texas... 220 100 WABW Wooster, Olio 248 50 WE MC Berrien Spas., Mich 484 1000 KFE Y Kellogg. Idaho 232 10 KGRS Amarillo. Texas.. . 244 "250 WABY Philadelphia. Pa 248 50 WENR Chicago, III 288 500 KFGQ Boone. Iowa 210 10 KGTT ;gun Francisco, Calif .. 207 511 WA BZ New Orleans, La 238 50 WEPS Gloucester, Mass 297 100 KFH Wichita, Kan 240 51X) KGU Honolulu. I(await 270 60(1 WA DC Akron, Ohlo 238 1000 W EV D Woodhaven, N. Y 246 500 KF HA Gunnison. Calo. 4 511 KG W Porl land. Oregon 492 100(1 WA FD Detroit. Mich 221 lilt) W E W St. Louis, Mo. (day) 353 1000 KF HL Oskaloosa. lov 213 111 KGY Lacey, )Cash 244 ill WAGM Koval Oak, Mich 225 50 WFAA 1)511as, Tees 545 500 KF I Los Angeles, (t:dlf 168 5001 KHJ Los Angeles. Calif 41)11 1000 WAIT Taunton. Mass 214 10 WFAM St. Cloud, Minn 252 10 KF IF Portland, Ore 214 50 (Also 11)4.1 meters; 501 watts) iCulumbu`.e_OLio 253 W FAN Philadelphia, Pa 224 500 246 KHMC Harlingen. 236 100 wéó 101) WFBC Knoxville. Tenn 234 ' KF 10 Spokane. Wash 10) Tex Appleton, 50 KFIU Juneau. Alaska 22:. 111 KH Q Spokane. Wash 371) 11100 WALK Willow Grove, Pa 201 51) WFBE Cincinnati, Ohlo. 246 250 KFIZ Fond du Lae. Wis -'158 1111 KIC K Red Oak, Iowa May) 3_2 100 WA M D t\linneapolls, Minn 222 1090 WFBG Altoona, Pa 268 100 KFJB 'Larsoállown, Iowa 248 "10) KJ BS San Francisco. Calif 220 50 I .Auburn, Ala 341 1000 WFBJ Collegeville, Minn 273 - 100 KFJ F Oklahoma (Sty. Okla 273 750 (1)XÁ It, 33 meters; 50 tvalts) WASH Grand Rapids, Mich 256 250 WFBL Syracuse, N. Y 258 750 KFJ I Astoria. ore 250 15 WFBM Indianapolis. Ind 275 1000 KFJ M Grand Forks, N. 1) 333 10) WFBR Baltimore, Md 244 100 KFJR Portland. Ore 283 11X1 WFBZ Galesburg. Ill 248 50 KFJ Y Fort Dodge. I Ows 232 100 WFC 1 Pawtucket, It. I 242 10) KF12 Fort Worl h. Texas 250 50 T1IE list of broadcast stations here presented is in ac- WFDF Flint, Mich 273 100 KFKA Greeley, Colo 20 21X1 WFI Philadelphia. Pa 405 500 KF KB Milford, K:ulsls ''42 +1510 cordance with the temporary licenses issued by the W F I W I lopkinsville, l(t'n 261 750 KF KU Lawrence. Kansas 254 51X) Radio Commission; and subject to the possibility of minor WFJC Akron, Ohio 227 KFKX Chicago. III '520 2506 WFKB Chicago. Ill 224 500 KF KZ Kirksville. Missouri.... 225 15 adjustments being made by that authority, will remain in WFKD Philadelphia. Pa 248 50 KFLV Rockford. III. 2118 10() force until April 1, 1928. WFLA Clearwater. Fla 517 750 KFLX Galveston, 'Texas..... 270 101) WGAL Lancaster. l'a 252 15 KF MR Sioux City, low'a. 2:72 116 WGBB Freeport. N. Y 246 400 KFM X Northfield, \Ilan 230 5X01 WGBC Memphis, Tenn 229 15 KFNF Shrnandnah.hwva(day) 461 210) WGBF Evansville, Intl 236 250 Bout le, \\ash 349 2500 WATT Boston,Ma8s(Iortable) 201 11)0 I KFOA Searle. Wash . 447 10001) KJR W G B Scranton. Pa 231 250 KFON Long Beach. t'alif..... 212 58) (Also 105.2 meters; 5 to 250 watts) WBAA West Lafayette, l ná..273 5)10 WGBS tNew York, N. Y 349 500 Seal \Cash 2)15 1a5 Harrisburg, Pa. (day). KFOR Lincoln. Neb 217 11)11 K KP tic ..... WBAK 300 501 WGCP Newark, N. J 268 250 KFOX Omaha. Neb 258 101 KLCN Blytheville, Ark. (clay) 285 51) WBAL :Maltimore, Md 285 5(100 WGES tCllieago, Ill 242 500500 KFPL Dublin. 're o,s 275 15 KLDS Independence, Mo 270 1500 WBAO Decatur. Ill 21.8 100 WGHP fMt. Clemens, Mich 278 KFPM Greenville. Texas 231 I5 KL IT Portland, Ore. 207 10 WBAP Fort Worth. Texas 500 5000 W G L tSeeaucus, N. J 294 1000 KFPR Los Angeles. ('alit... 232 25(1 K LS Oakland, (Á111f 246 250 W BA W Nashville, Tenn 240 500 WGM Jeannette, Pa 208 50 KFPW Carterville, MO...... 263 50 KLX Oakland, calif 508 500 W BAX Wilkes Barre, Pa 250 100 WGMS Minneapolis, Minn 246 500 Spokane. Wash 2)6 250 KLZ }Dupont. Calo 35:3 "75A1 WGBC Brooklyn. N. Y 227 500 WGMU New' York,N.Y.(port ) 201 100 KFPY 395 1000 (7X:\11. 105.9 mewl,. 511 watts) KMA Shenandoah, Iowa WBBL Richmond. Va 23.1 100 (Also 106 meters, 50 watts) KFQA St. I.Onls, MO 234 50 KMBC see KLDS WBBM tGlenview, III 389 5000 WGN -WLIB Chicago and Elgin, Fort \Vert]. Texas :533 100 KMED Nledford, Oregon 250 50 WBBP l'etoskey, knell 240 100 Ili 416 15,000 KFQB IC 224 250 ...... KFQD Anchorage, Alaska :545 11)11 KM Inglewood, Calif WBBR Rossville, N.Y 256 1000 WGOP Flushing. N. Y 200 100 Calif 250 100 KMJ Fresno, Calif ... 366 50 WBBW Norfolk. Va 236 100 WGR Buffalo, N. Y 303 KFQU Italy City. "250 _. 750 (Also 31, 5:1. 03. 105 meters. 51) watts) KMMJ Clay Caner, Neb..... 2S5 W B B Y Charleston. So. Car 250 WGST Atlanta. (la 270 500 KFQW Wenatchee, Wash 217 100 KMO Tacoma. Wash 254 250 WBBZ Chicago, Ill. (portable) 204 1ÓÓ WG Y Seh'ncetady. X. Y.....380 50,000 KFQZ Hollywood, Calif 33.2 100 KMOX 1St. Louis. Mo 3(X) 50(0 WBCN Chicago, Ill 288 250 (Also on 32.77. 21.06 and sometimes (Aso 108.2 meters. 50 watts) KMTR Los Angeles. Calif 526 500 WBES Takoma Park. Md 265 100 5 meters) KFRC San Frtnesco, Calf 451 1000 (Also 108.2 meters: 250 walls) WBET :Ie.lfnrd, Mass 2S8 500 WHA :Madison, Wise 333 750 KFRU Columbia, Missouri 250 500 KNRC Santa Montes Calif 375 500 WBIS See WNAC WHAD Milwaukee. Wise 270 500 KFSD San Diego. Calif 441 501 (Also 1118.2 meters: 100 watts) WBKN Brooklyn, N. Y 200 100 WHAM Rochester, N. Y "280 5000 Angeles. Calif 27 1 fá)0 KNX Los Angeles. Calif 437 500 WBM H Detroit, 5110)1 211 (ins short -wave transmitter) KFSG Los 100 walls) 100 (H(Has short-wave transmitter) (Also 107.1 meters; WB MS Union City, N. J 200 100 WHAP tCarlstadt, N. J...... 236 1000 Galveston. Texas 258 500 KOA Denver. Colo " "320 "2500 W BN Y New York. N. Y 36 500 WHAS Louisville. Ky 422 500 KFUL Oregon 271) 500 KFUM Ooloradn Sp -s. Colo 2S3 118011 KOAC Corvallis, WBOQ Richmond 11111. N. Y 309 5t)0 WHAZ Troy, N. Y. (Monday) 306 500 KFUO tClavton. Mo 5.15 10110 KOB State College New Mex :3951 5007 WB RC Birmingham. Ala 242 250 WHB Kansas City, Mo 341 500 Colo 2.27 100 KOCH Omaha, Nob 254 250 WBRE Wilkes Marre, 250 WHBA Oil Clty, Pa 261 10 KFUP Denver, Okla 252 250 l'a 100 Utah 225 516 KOCW Chickasha. WBRL Alton. N. 11 232 WHBC Canton, Ohio 36 10 KFUR tFarmington. KO 319 5(100 500 KFUS Oakland, Calif.. 256 511 IL Counell Bluffs. Iowa t1 XY. 105. 109 meters, 250 walla) WHBD Bellefontalne, O 222 100 Utah 250 511 (0XU. 151.015 meters, 500 watts) WBRS Sec WHBF Rock Island, Ill 222 100 KFUT Salt Lake (Ie,. Oregon 319 1000 WCDA 218 250 1(01N tPortland, WBSO 31.44 WHBL Chicago, Ill. (portable) 204 100 KFVD Venlrr. Calif Seattle, 316 1000 Wellesley Dills. Mass. 100 (Also 105 meters. 51) watts) KO MO Wash ..... WBT Charlotte. Nn. Car 25S 750 WHBM Chicago. Ill. (portable) 201 100 KFVG Independence, Ian 225 50 KOW Denver, Colo 248 250 W BZ tSpringneld, Maas. 333 15,0 WHBP Johnstown. Pa 229 "250 234 1:1 KPCB Sel t le. \\:ash 241 50 short WHBQ Memphis. Tenn 232 100 KFVI Houston, 1'rxaa...... , KPJ,t1 214 15 (Ilse -wave transmitter) KFVS Cape Girardeau. Mo.'221 :5:1 Pre,eott, Ariz WBZA 1)0,10,1, 51114s...... 333 500 W H B U Anderson. Ind 220 l5 301 FIX) KPLA Los Angeles. Calif 2 500 WC AC Mansfield. W HB W Philadelphia. Pa 220 100 KFWB Los Angeles. Calif..._. 211 101 (',,nn 535 500 105 and 41) meters. 50 tvát ts) KPNP Muscatine. IOWA Canton. WHBY West De Pere. Wis 250 50 (Also San 422 1106 WCAD N. Y 244 "500 KFWC Glendora, Calif 222 100 KPO Fnlwcise°. Calif WC AE Pittsburgh. Pa 461 500 WHDI Minneapolis. MIinn 246 500 KFWF St. Louis. Mo 244 251) KPPC Pasadena, Calif 229 51) Columbus. W HEC -WABO Rochester, N.Y 254 500 KP RC Houston. 294 500 WCAIi Oho 23.1 250 KF W I Saul Francisco. Cal 25S 500 Trias WCAJ TJneoln, Neb. (day) 380 50) WHFC Chicago, III 216 200 236 510 KPSN Pasadena. Calif 316 1000 WH K Cleveland. Olio 265 "500 KFWM Oakland, Calif 270 50X) WCAL Northlleld, Minn 28(1 500 KFWO Avalon, Calif...... , 300 259 KQV Pltts Pa. WCAM Camden. N I .24 500 (Also 66.04 meters. 500 watts) Jerome. Idaho 204 15 KQW 5.111.Jose. Calif 297 510) WCAO WHN New York, N. Y...... 395 500 KFXD KRAC Shreveport. 1.5. 220 50 Baltimore, Md 214 250 KFXF Denver. Coln 283 2511 WCAP Asbury Park, N.J 240 500 WHO Des Moines, Iowa .... 535 5000 500 KRE Berkeley. Calif. 256 100 WHPP Englewood, N. J 205 10 KFXJ tIde,water.Cnlo.()cw)2l0 461 50) WCAT Rapid City, So. Dak 218 1011 KFXR Oklahoma City. Okla 22-1 S) KRLD Dallas. Texas.. WHT 1Chicago. Ill '300 500) KRLO 1.ns Angelis. Calif 216 250 WCAU Philadelphia, Pa 261 500 KFXY Flagstaff. Ariz 205 :25 WCAX Burlington. Vermont 254 100 W IA Philadelphia. Pa 88 100 KF YO Hnmkenridge. Tex 211 15 (6XA N. 11159 meters, 250 wtts) W KAS Ottumwa, Iowa (day) 322 116 KRSC Seattle. ]\'ash 211 50 WCAZ Carthage. Ill .541 50 W IBA \Vis KFYR Bismarck. No. Dak 250 2:0 1011 Madison. 240 100 -s 333 500 WC BA Allentown, Pa 222 KG A 2111 21111:1 KSAC \Lanhnl tan. Nand WIBG Elkins Pk..Pa.(Sund'ys)441 0 Spokane, Wish I 11000 WCBD /loll, III 345 5006 KGAR T,esn,,. Ariz... 231 1110 KSBA tehrevelmrt. a 268 New Orleans, WIBJ Chicago, Ill. (port.) 201 100 KSCJ Sioux C3t4'. Iowa 244 "500 WC BE l.a 227 W IBM Chicago. (port.) KGBU Retrhikan, Alaska 416 NY) WCBM 1tallImore, M d ? 100 Ill. 201 100 III(] KSD St. Louts. Mo 545 500 WIBO iChieago. 111 406 5000 KGBX St. Joseph, 'In.. 248 333 250 WC BR Providence, R.I.(port ) 201 100 KGBY Columbus, 212 5 KSEI Poeatello, Idaho W IBR Steubenville. Ohio.... 250 50 Nebraska KSL Salt Jake City. Utah 30.3 1001) WCBS Springfield, III 2111 250 KG BZ York. Nebraska 213 111:1 WCCO iallnncloolls, WIBS Elizabeth, N. J...... 204 250 Santa , 11)0 Minn....105 "500 KGC A 10 KS M R Matrla, Calif.. 273 WIBU Polnette. \Vis 217 20 Deeoral. Iowa... 2I: KSO Clarinda. Iowa. 2 7 500 WC DA-WBRS KGCB Okla 21 6 .... W IB W Topeka. Kan...... 204 250 Oklahoma City. So. 210 "250 Cllffside, N. J . 211 250 KGCH 211 KSOO Sioux Falls. Dak WIBX Utica. N. Y 238 150 Wayne. Nebraska 291 KSTP St. Paul. Minn. 222 "2000 WCFL Chicago, Ill 484 1500 1Ó1n WIBZ - KGC I Sam Afltomdo, Texas 220 WCGU 21:1 500 'Montgomery. Ala 231 15 KTAB Oakland. Calif 280 506 Brooklyn, N. Y W IC Easton. Conn 265 KGCL Feu tir, 1\aeh. 231 San Also 54 meters. 150 watts) KGCN 511 KTAP Antonio. Texas 229 20 WIL St. Louis, än 258 250 COOIONIIx. Kansas 208 KTBI Las Angelo. Calif 288 500 WC LO Kenosha. Wise. Inn KGCR Brookings. So. Oak 208 15 W IOD Miami Ile ell, Via. 248 1000 KTBR Portland. Oregon 283 50 WC LS Joliet, Ill 216 51111 WIP KGCU Mandan. No. Dak 240 110 Culver, Philadelphia, Pa 399 500 KTHS Flot Springs. Ark....3S4 "000 WCMA Ind 261 (O WISN NA KGCX Vida. Montana 2_44 llilw'aukee, Is '270 250 KGDA KTNT Muscatine. tows 6i 2000 W CO Pensacola, Fla 250 516 W IVA Norfolk, Vs 210 100 Dell Rapids. Sn. Dak. KTSA San Antonio. Texas 265 2000 WC OC Columbus. Miss 231 250 15 WJAD Waco. Tex 333 500 (daytime) 254 KTUE Houston. Texas 213 5 WCOT tOlneyville. R. I 225 100 KGDE Barrett Minn 205 50 WJ AG Norfolk, Nell 285 250 KGDM KTW Seat )le. Wash 395 10(0 WCRW Chicago. III 224 500 WJAK Kokomo. Ind 234 50 Stoektnn Calif. 217 10 WCSH Portland, M01nr 366 5)10 KGDP KUJ Seattle, WW1 200 10 WJAM Cedar Rapids. Iowa, 240 250 Pueblo, Coln.. ?24 10 KU OA I'ayel teville. Ark 297 500 (Also 63.79 meters, 250 watts) WJAR Providence. R. I. 484 500 KGDR San Antonin. Texas 207 15 KUOM NILsnula, Mont 461 11!X1 WCSO Springfield, Ohio 256 500 WJAS Pittsburgh, Pa 270 500 KGDW Humboldt. Nob 294 100 KUSD Vermillion. So. Dak 484 250 W C W K Port Wayne, Ind 214 250 WJAX Jacksonville, Fla 441 1000 KUT Mott in. Tessa 232 500 KGDY Oldham. So. Dak 207 15 WC WS Danbury, Conn 265 100 WJA Y Cleveland, Ohio 227 500 KV I Tacoma. Wash 234 510 WJAZ. Prospect, 263 5000 KGEF T.os Angeles. Calif 263 500 WCX See WJR 'Mt Ill KGEH KVL Seattle. Wash .... 203 100 WJ BA Joliet. Ill 2-18 50 Eugene. Ore 201 50 KV OO .Tulsa. Okla 349 1000 WDAD See WLAC o WJBB Sarasota. Fla 238 250 KGEK Yuma, Colo 263 10 KVOS Bellingham. Wash 210 50 WDAE Tampa. Fla 265 500 WJBC LaSalle, Ill 227 100 KGEN El Centro, Calif 225 15 KWBS Portland. Oregon 200 15 WDAF Kansas City, Mo 370 1000 WJBI Red Bank, N. J 263 250 KWCR Cedar Rapids. Iowa 240 250 KGEO Grand Island. Neb 205 100 WDAG Amarillo, Texas 26.3 250 WJBK Ypsilanti, Mich.. 220 15 KGEQ' KWEA Shreveport. La...... 213 250 Minneapolis. Minn 204 50 KWG Stockton. Calif 345 50 WDAH El Paso, Texas 234 100 WJBL Decatur. Ill 213 250 KGER Long Beach, Calif 216 100 KWJJ Portland. Ore 229 50 WDAY Fargo. No. Dakota 545 TASO WJBO New Orleans, La 263 100 KGES Central City. Neb 204 10 (Also 53. 54 meters, 100 watts) WDBJ Roanoke, t'a... 231 250 WJBT Chicago, BI 389 500 "Allowed higher daylight power, ...Standard or 0Onstant- frequency transmission. (Remote Control. (Continued on page 1147)

www.americanradiohistory.com 1." Radio News for April, 1928 "Weighing In" Radio Stations

â Description of Easily -Constructed Apparatus That Will Tune in Different Radio Stations by the Addition of Weights on a Balance

1 By A. Binneweg, Jr.

lll, -Marconi of our college was Philip in the laboratory, Randall would welcome inviting a number of students to a part) Randall; he was a young man, not the company of students, who were inter- at his hone during the coming week. over twenty -five years of age, who ested in his work, as often they would be Everyone was in the best of spirits on T had recently received his E.E. degree. able to assist him and cheek his results. the evening of itandall's party. Six men IIe had been promised the first vacant During the period we are describing, be who were particularly interested in radio assistant- professorship in the electrical de- acted peculiarly, in this respect also; when had been invited and they were accompanied partment and, while waiting for this open- anyone would enter the laboratory he world ing, he had accepted the position of labora- quickly cover up his work and plainly show tory assistant. He was kept very busy that he did not desire company. When ques- with his official duties during the day but, tioned about Its work he would avoid giving frequently after dinner, he would retire to any details, but promised to give a demon- a corner of the laboratory and experiment stration of his invention when it was with new radio apparatus of his own in- complete. vention. Often a light would be noticed A few days before the Easter vacation in tho laboratory during the early hours a complete change came over Randall. He of the morning and everyone knew that "icmed anxious to join everyone in having 1tandall was occupied in perfecting some new radio device. From Our brief dcscriptbat of Philip Randall, we do not wish you to gain the impression that he was cceetdric; for he was not. Randall was well -liked among the students of the college and was popular also with the fair sex. On the nights when special dances were held he was ulvays to .i:etch illustrates the manner in a-i. ir!: .. he found in the crowd, and he was present balance is attached to the spring coil. at all athletic events of importance. Par- ticipation in the rehearsals of the glee club by an equal number of girls frown the a i1y was another college activity which he en- itself. In the early part of the evening they joyed greatly. However, he had always played bridge; Eder the tables were removed saved at least three or four evenings each and they danced to the tunes of an electric week for experimenting in the laboratory, phonograph; and, afround 10:30 P. VI., re- and during the course of a year he world freshments were served. After all had fin- develop ninny very interesting receivers. ished eating it was suggested that radio music would finish up the evening in great THE PLOT THICKENS style. 'Phis, it scented, was exactly what It so happened that, for over a month Randall had been waiting for as he stood prior to the Easter vacation, Randall a.p- tap in preparation for making a speech. peared to be very busy with his radio ex- periments, and most of his associates ac- A REMARKABLE DISCOVERY cused him of icing unduly secretive. It "Ladies and gentlemen," he began, "for was noticed Ilat he had not been present the past several weeks I have been spending at three consecutive meetings of the glee my on new "Raadail selected a weight, placed it on the all spare tinte a invention which chub and that he had left the Saturday eve- scale . . . and the signals were heard coning may revolutionize the entire radio industry, ning dance before II O'clock. In addition from the speaker." and tonight I will demonstrate to you a re- to these suspicious circumstances, a light markable receiver which exemplifies my new was seen hunting in the laboratory every a good tinte and was glad to be included in deas. In my experimenting I have found (`vening. all social activities. He accepted several that there is a distinct relationship between !'snp, when busy with his experiments invitations to parties and surprised all by wavelength and weight, and, with the danta which have been discovered after hundreds of tests, I have been able to develop an entirely new system of tuning. With this receiver, a different weight is used for Inning in each station. When this method is used the owner does not have to learn the technique of tuning, but has merely to se- lect a weight which is marked with the call letters of the station he wishes to hear. 'l'1 is weight will automatically tune in the pro- gram. Now, gentlemen, if yon will assist me, I will remove the set from the closet." When the closet door was opened all per- sons in the room could see the apparatus which was to he used in the demonstration. There was a large table and over it a cover which extended almost to the floor. On The schematic diayrana of a receiver which employs for a loop antenna a spiral spring one end of the table there *as a small radio which is tuned lo its stretching tinder the strain of different weights. (Continued on page 1159)

www.americanradiohistory.com Radio .\ ez s for April, 192S 1123 Whispering Across the Hudson River

A Loud Speaker with 30 -Watt Distortionless Output, which Can be Heard Over a Distance of a Mile

By Joseph Riley

NE of the most rigorous tests to which a loud speaker has ever been .1t for left the top plates .subjected was recently performed of flrr unit have been re- moved, showing its inte- in New York City by engineers of rior. Below, right, the the Bell Telephone Laboratories, when they diaphragm and coil of it u the speaker; the detached instilled giant speaker on the roof of coil shows the method of thirtern -story building on the New York minding the tine aluminum side of direct com- strip. Insulation is pro. the Hudson River for vided by a layer of var- munication with the Jersey shore, which nish, .0602-inch thick. The is over a mile distant. Eiugínee.s on the proximity of Be coil to the pole pieces lias a bene- opposite side of the water lienrd both music ficial cooling action. and voice reproduced with enormous vol- ume, but without distortion. 4131q13111131.,1111111111111 iiii It ii iii :i,:1.1,.11 (Continued on page 1167)

.Ibovc, the completely-asscrnlded land-speaker u lilt : Icco of tiro binding posts are connected to the moving coil and the other pair to the ends of the electromagnet's windings.

THROAT LEADS TO HORN PLUG PREVENTS RESONANCE DIAPHRAGM AND ATTACHED CO/L, LATTER CARRYING VOICE FREQUENCY CURRENTS

DRIVING COIL THESE WINDINGS CARRY STEADY CURRENT FIG. I Above is diagramed the assembly of the new loud -speaker unit; the diaphragm with its attached roil works like the plunger of a pump, at high (inedia) frequencies.

:It the right, the two horns used in the tests across the Hudson River; nine rants were used on the smaller one. Both are of the exponential type, giving ma.rimn In range and quality to the transmission of sounds.

www.americanradiohistory.com 11U4 Radio News for April, 1928

What a Radio Tube Is, and What It Does By Clyde A. Randon

THOItOUGH understanding of the special composition which usually becomes functions of the vacuum tube, the "incandescent" when in operation, but not heart of broadcast transmitting and necessarily so. Some filaments must be A. receiving apparatus, is of funda- heated to incandescence (glowing white- mental importance to the radio beginner if ness) for best results, while others perform he wishes to understand even the most ele- more satisfactorily when operating at a mentary principles under which his equip- cherry-red heat; different filaments require ment operates. Aitid es explaining the action different temperatures for highest efficiency, of these tubes have been published many Ind all operate in a similar manner. A fila- times in this and other magazines; but they ment may be looked upon as composed of have been usually so technical that the ordi- a "volatile" substance, which evaporates nary listeners, the rank and file of the vast when heated and thus gradually disappears. audience which now enjoys the pleasure of Water at ordinary room temperatures, for radio entertainment, find considerable diffi- example, evaporates slowly but, as it is eulty in apprehending the meaning. Too heated, more and more evaporates; and O often a valuable article is made puzzling for finally there is violent "ebullition" (boiling) HG. 1 them by the presence of electrical terms and the water becomes steam and passes which, though elementary, are not frequently into the atmosphere. The action of evapor- At A nee have no current in the filament, no used in ordinary conversation. ating water and the escape of particles of electrons evaporating. At B, with the battery switch closed, the filament is lighted and from In this article the writer will attempt to matter from a heated filament are very it electrons in countless billions are escaping. explain the operation of a vacuum tube, similar. - (See Fig. 1.) in language which the average reader is cash other, and in a liquid or gas they are able to understand; and he will avoid, as traveling in random directions. If a body far as possible, the special terms used by is heated, these molecules speed up and scientists. Of course, it will be impossible thus bombard their neighbors with greater to explain here some of the more compli- velocities. At high temperatures, ( "high" cated applications of radio tubes, as these for one substance may be "low" for others; require a fundamental knowledge of radio this is only relative) the molecules reach circuits in order to learn what takes place; such velocities that some are capable of Ind the way in which a tube functions as breaking away from the influence of the an amplifier will be described. This is the others, and thus pass away from the sub- use of the majority of tubes in radio re- stance, in the form of vapor; that is, ceivers and, therefore, this explanation "evaporation" takes place. should clear up ninny problems which per- Due to the influence of neighboring iurle- plex the naincl of the beginner. At .i, the "B" battery switch is open, and the electrons gathered in as aimless crowd around cules, there is a tendency on the part of the filament. Al B the plate is POSITIVELY a solid or liquid substance to "cohere," or USE OF TILE FILAMENT charged by connection to the " +" of the "B' hold on fo its constituent parts. In the case battery, and electrons are attracted in a steady .1 tube consists of a filament, a grid and stream from filament to plate. of water, for instance, there is what is ai. plate, all "hermetically" scaled in an called "surface tension "; that is, the surface "evacuated" bulb, which is provided with All substances are composed of almost in- of the liquid acts like a stretched membrane, convenient external terminals for making conceivably small particles called "mole- and it is thus made more difficult for mole- contact with these three "elements" inside. cules." A t ordinary temperatures, these cules to escape (or the liquid to evaporate) The filament is simply a thin wire of small bodies are continually colliding with oat ordinary temperatures. (One can easily perform a simple experiment in this con- nection. A small needle can be made to float by laying it carefully and perfectly flat on the surface of a glass of water; ihns showing that there is "surface tension." 'l'he needle must be perfectly dry or even oily; otherwise the water will "creep" around the needle and it will sink.) "EVAPORATING" THE FILAMENT If water is heated, the molecules reach such velocities that the surface tension is no longer strong enough, and they simply break through in large numbers and leave the liquid -as we have explained, evaporate. This is almost exactly what takes place in a heated filament. At high temperatures .4t .4, the disconnected grid has little erïcet on the electron flnc, from filament to plate; but at B (very much greater than the boiling-point the " +" charge on the grid adds attraction and greatly increases the flow. Ott the contrary, the of water, of course) the velocity of the charge on the grid shown at C, veil! drive back the electrons and let few or none reach the plate. "electrons" or particles of negative dee-

www.americanradiohistory.com Radio /\ ems for April, 1928 1125

had their choice of two guesses and they guessed wrong. To this day, this erroneous This diagram shows the simplest way to "hook cup" assumption is still prevalent, in common n tube to make a radio speech, just as we say "the sun rises;" but receiver. The ".I" bat- tery lights the filament; if the reader will remember that the elec- the "B" battery 'puts trons proceed from filament to plate, there volts at" the plate and need be no confusion in his mind. causes a flow of current, the changes in which are heard in the phones as sounds. The "C" bat- THE ELECTRON- CONTROL GRID tery puts on Elie grid the voltage, commonly called a "bias," which is needed By introducing a third element, called because this tube ,must be for short a "grid," the stream of electrons n "detector" (see page 1151) as well as an "am- between plate and filament can be con- plifier." A pictorial dia- trolled. 'l'he grid consists only of very line gram of this one -rube set wires, spaced definite distances apart will be found on page at 1168. so that a large proportion of the electrons can pass between them. Just as the posi- tive charge on the plate tends to cause a flow of electrons from the filament, so a tricity in the filament becomes so great that positive charge on the grid will also tend they simply shoot out into the surrounding to increase this flow. (See Fig. 3.) with relatively large velocities. n,,,,,,,,,,,,,,11,,,,,,,,,,. , FREE,,,., t muwmwwwuwe space, The grid, however, is much nearer to time If another element (such as the "plate," filament than the plate is; and any charge were found in nil radio vacuum tubes) or "voltage" on the grid will thus have a filament, insulated placed around the but Blueprints much greater effect on the electron flow from it, some of these electrons would strike than an equal charge on the plate. A nega- the plate; the rest would tend to form n tive charge on the grid will decrease the "cloud" :wound the filament, sonic electrons BEGINNING with this notice, lt.\mo NEws will give away, free, electron flow to the plate (the "plate cur- leaving the filament and others again en- rent") and the amount of decrease will de- tering it. (This "space- dinrge" effect is complete blueprints for sets described in the constructional articles that will pend upon the strength of the charge on illustrated, and explained, on page 846 of the grid. RAmo NEws February, if any readers be printed in its pages, heginning for It is readily seen, therefore, that the grid to follow further.) A condition with the April issue. iIluep.itnts of desire it acts as a delicate control of the plate cur- approaching equilibrium would be reached; sets published previous to the April rent. Since a very small charge on the that is, there would be the sanie number of issue are not offered free. grid has a relatively large effect on the the new policy of RADIO electrons leaving the filament as returning, Under 'plate current, the tube "amplifies" the useful occur. NEWS, no mauntfauturers' names nor and no result would (See small electrical impulses which are "im- marks are given in the text 2.) trade pressed" on the grid. Very- small effects If, however, a positive charge (compared pages of Remo NEws. For the infor- thus give large response. with that on the filament) or voltage is mation of those who wish to construct placed on the plate, electrons will flow to sets and power packs, however, and to the plate and continue to do so as long as facilitate their work, the blueprints USE IN A RECEIVER the filament is heated and the positive will contain complete specifications of euargc maintained; since electrons consti- all the material which is used in rak- In the simple circuit shown in the dia- tute negative electricity, they are attracted ing the complete apparatus described grams, the tube is used to amplify the weak by a positive voltage (for unlike electrical in the constructional article. These "signal" impulses which arrive from a A. induces charges attract each other.) blueprints will be given free to read- broadcast station. passing wave a small in the antenna and ers who apply- in person at the office current this THE ELECTRON STREAM of lt:uno News, between the hours of flows through the coil between the aerial ground. (Note the current oscil- In the vacuum tube, when connected in 9:00 a. in. and 5::30 p. m., daily. Those and that lates [reverses its direction, back and this way, there would thus be a cont in lions who apply by mail should enclose ten forth between aerial and ground and, flow of electrons, and this constitutes an cents, for postage and mailing only. the there- fore, for best results the ground connection electric "current" It is to be noted that Address Blueprint Department, RADIO nmst be well -designed also). 'l'he current such a stream can proceed in only one di- NEws, 230 Fifth Avenue, New York in the primary coil gives rise to a 'magnetic rection, from filament to plate- negative to City. positive. It is often said that the current field, which induces another current in the travels from positive to negative, and this secondary. This gives rise to a difference is because in the early days the scientists (Continued oie page 11651

Above wo have several of the steps in the assembly of a plate and the grid. The four following views ,show suecessire vacuum tube. At the left: above, the filament; below, the - stages of manufacture.

www.americanradiohistory.com 1126 Radio News for April, 1928 An R. F. Short -Wave Broadcast Receiver* (Awarded $100.00 Monthly Prize -See page 1119) Incorporating an Optional R. F. Stage, Interchangeable Coils for the 10- 725 -meter Bands, and Push -Pull Amplification

By W. Francis Goodreau

WA below 200 meters ENORMOUSLY GREATER RANGE peciall when unusual programs are being arc rapidly becoming established Not only in the United States, but in a offered. Practically all of the short -wave as channels for the broadcasting number of other countries (including Eng- stations in this country broadcast the same of radio entertainment. The re- land, France, Germany, Holland, etc.) many program simultaneously on their broadcast cent announcements of the decision of a stations are broadcasting on waves between and short -wave transmitters. to number of popular broadcast stations 30 and 200 meters. A majority of these Because of their musical excellence, these operate special transmitters on these waves programs, even those originating on the programs are interesting to every faith listener, proves that the industry's growing and especially to the DX fan who, having in transmission on high frequencies is be received practically all of the American and ginning to be manifest in a concrete form. Canadian stations, is looking for new worlds On the other hand, the interest of the gen- BECAUSE of the demands of read- ers for the constructional article to conquer. Unfortunately, until recently eral public in the construction of short- it was not possible to hear the short -wave wave receivers shows that the special pro- on a short -wave receiver which it con- tained, the issue of RADIO NEWS for broadcasts with any degree of satisfaction, grams which are being transmitted on waves because of the lack of suitable receivers. outside the broadcast band are being October, 1927 has been completely ex- hausted. To satisfy the many people The sets that were used were mostly de- a ppreciated. signed for code reception and, although they waves have from who want to get into the short-wave Short many advantages, were very efficient, they were not designed the viewpoints of both the broadcaster and "game," we are presenting herewith a second article describing another short- to give the quality of reception demanded the listener. In the first place, they seem of broadcast receivers to -day. to be more efficient, as the programs of wave receiver of excellent design. We low -power stations are frequently heard earnestly recommend it to our readers Recently, however, articles have appeared half -way around the world. Secondly, there who wish something new.- Enrron. in a number of radio magazines describing is less congestion, as more individual chan- the construction of sets designed for quality nels arc available; and, as a result, a listener of tone reception on short waves. 3lost may often receive the program from the other side Of the Atlantic, arc available to strictly -short-wave receivers use condensers short -wave transmitter of a station with the owner of an efficient short -wave receiver. of very small maximum capacity in order less interference than would be experienced A number of these stations are broadcast- to tune to the short wavelengths. "When in receiving the same program broadcast on ing on regular schedules, while a great num- receivers of this type are used for the re- The regular waves. ber are "on the air" quite frequently, es- ception of waves above 200 meters, it is

This picture shows the location of practically all parts used in formers; 171, 1"2, V3, 1'4 and P5, tube sockets; Cl, C2, tuning the construction of this short -ware receiver; the symbols condensers; C3, regeneration condenser: R2, R3, R4 and R5, correspond to those used in the zoiriag diagrams and the list filament ballasts; RG, volume control; PH, oscillation control, of parts. Ll and L2, R.F. coils; Tl, T2 and T3, audio trans- Rw, switch controlling R.F. amplifier stage.

. RAPTO NEWS Blueprint Article No. 52.

www.americanradiohistory.com Radio News for April, 1928 1127

Inenter will find it easy to construct accord- ing to his personal desires, since a wide SIDE VIEW END IEW number of types of tubes can be used in the set. If it is not so desired, the audio - frequency end of the circuit need not be of er the push-pull type; although the quality of reception will probably- be somewhat better if this type of amplifier is used. Another point in favor of this receiver is that, al- Go though it complete equipment of coils to cover all the wavebands over which the FLEXIBLE WIRE set is capable of operating would be rather expensive, the constructor may purchase 1- .Iq .. ...,=b HINGE 'Ia the coil mountings and two coils for the -'I.,o. short -wave band at which the receiver is to be operated most frequently, and add the I ; I- 11 p other coils later when finances permit. This _,:=- feature alone is a good indication of the fal li 11 IIL_J-I-1 flexibility of this receiver. . .. . i ,.. With the panel and sub -panel drilling 16 11 ' I tK I ,r.. layouts shown here, it will be a simple mat - I i I s-I16 ter to place the various parts in their proper 3 I I I positions. will be noted that. although ',VI It 8" NO. i i COIL i. 2. 3.! 4. 5. 6. the front panel measures only 24 inches long, 2s k +t? 1 ZJ I 1 16 141 2 3 8 119 40 94 the spacing center to center the I from of 76 1 I SECONDARY COIL I WIRE variable condensers is 8 inches; more than SIZE OF 18 18 18 18 24 24 ON SECONDARY the usual spacing of such instrununts. Be- INSULCONATION IIIIIIIIII` ,J E E E E SSC SSC cause of the short wavelengths to which 1 ON SECONDARY .-T I 7y !IIIIII,IIIIII y,t. r LENGTH OF t A 1" 3.. 2g7 this set can be tuned, this spacing WiS F4,1 t 11 1L. 1 1 2 I8 .r-!^!1er;- SECONDARY 8 I" deemed desirable to prevent interaction be- TURNS ON 2 2 4 6 15 20 TICKLER COIL tween units and eliminate any need for 111Inl 1111,11 11 ' SIZE WIRE shielding. 'l.'he coils are placed at right 28 28 28 28 28 24 ON TICKLER cash space is INSULATION angles to other and sufficient SSC SSC SSC 55C 5sC SSC lIIIIIII ON TICKLER left lid Weell them to assure correct LENGTH OF ! - 1 111'1 ,1:' 1 1 operation. TOP VIEW TICKLER iZ 3. 32 4 2 LENGTH In assembling the set, the sub-panel should 1 21 2d" 3" OMF 14 12 i- he drilled first and the apparatus mounted on it After this, the front panel should be I)iapranc gives complete details for building he six sets of coils required in order to drilled and the condensers (CI, C2 and C3) give This set n wavelength range from. III to "21 meters. The primary coil consists of volume control (116) and oscillation control 10 turns of \'o. 24. .S.C. wire wound on a fouls, 81/ inches in diameter, with whichever (l'I3) mounted. Care should be taken in set of coils it is used. laying out the panel and sub -panel, in order to get the holes at the right points; as otherwise considerable difficulty be en- necessary to use coils haying it lange num- receiver, suitable for use on any wavelength will ber of turns of Wire, in order to get an band merely by plugging in the proper coils. countered when mounting the apparatus. inductance value high enough to cover the By referring to the schematic diagram of After all of the parts have been moulted on the panel and sub- panel, the brackets Waveband Ilctwccn 200 aaul :5110 meters. this set, you will see that a stage of tuned should be screwed into place and the set 'While it is true that it tuned circuit having radio frequency has been placed before the is ready for wiring. The oscillation control it lange inductance and at small capacity usual regenerative circuit. Because of this will usually give loader signals from any additional tuned circuit, the receiver is very has been mounted on the front panel be- cause of the need of readjusting it with the given station than a smaller inductance and selective on wavelengths above 200 meters, different coils and tubes that will possibly large rapacity tuned to the saune station, even though shall tuning condensers are be used. it is also truc that the selectivity of the ulilircd. 'l'he audio -frequency amplifier has It will be noticed that a double -pole, circuit using the small condenser autel large been designed fur quality reception; it in- double- throw, jack switch (tiw) lens been inductance twill nut be as great IIS that of cludes one stage of straight transformer - incorporated in the set between the radio - the other combination. coupled and one of push -pull amplification. Thus, it Will be seen that this set combines frequency and detector tubes. This switch FAULTS OF E.tlel.Y DESIGN the advantages of both the broadcast and is for the purpose of comparing results obtained with the set when the radio-fre- It seems to have been the idea of the short -wave receivers in one flexible all-wave quency stage is used and when the set is designers, of most short -wave receivers, that circuit. operated as a simple regenerative receiver. these Were to he uscil entirely for reception CONSTRUCTION It is also helpful in adjusting the receiver of short Waves; and that it separate re- The set is so designed that the experi- when it is first tried out. ceiver would he used for the regular broad- cast band. While the use of plug -in coils will enable the operator of it short -wave receiver to cover the different hands, it will result in a receiver that is not very selec- tive above 2110 meters. The design of most of these short -Wove receivers is rather a step backward, when compared With the usual set used for broadcast reception; since prac- tically all of the sets designed for short - wave work are Of the plain regenerative. type. It attest be admitted that the use of two receivers has some advantages; but it roust also be pointed out that the cost of two receivers is beyond the means of many. Besides this, there is the requirement of PH additional space, not only for the receivers C3 but for the separate sets of batteries that would probably be used. This shows the arrangement of controls on the front panel of the set. Cl and C2, wave- 'l'he special short-wave receiver described length tuning dials; C3, regeneration control: PH, oscillation control: RG -Pit. SW, in this article Was designed to he a flexible volume control and filament switch. The plug -in coils are partly visible.

www.americanradiohistory.com 1128 Radio News for April, 1928

AER. R t' V4 L1 V1 V2 RFC T V3 T2 T3 G a 1 P G l' o o C4I 1vvv 1 o I :. PH C2 L.S. c_ : F F- GND. R2 B C T

R3 4 ,R5

FI L. SW

l fì6 AND FIL.SW. ON SRWAE SHAFT. o o C+ A+ B- B+67 V. C-AMP B+90V. C-POWER B+ POWER

This schematic wiring diagram gives complete details of all are used to identify them correspond with those in the other electrical connections in the receiver; and the symbols which illustrations, as well or the test.

Care should he taken in placing the grid Ind, the nearer you comic to the bunil be- of the second tuner further away from tue leak RI and grid condenser C4, to keep tween ?00 and 500 meters, the more inter - secondary. The relation of the primaries Them away from the plate wires leading ference will he experienced. I-Iowever, when on the tuning coils 1.1 and 1.2, to their re- to the radio- frequency tube (VI) and also the radio-frequency stage is connected in spective secondaries, governs the selectivity from the radio-frequency choke (1tFC) in the circuit, the selectivity is very good, on of the set. the detector plate circuit. The sub -panel both broadcast and short waves. It was found in testing the receiver that mounting brackets are placed as indicated; Having spent some time testing the re- different adjustments of the oscillation con- one slightly off center to provide additional ceiver in this manner, the aerial and ground trol (l'II) were needed for some of the support for the weight of the audio -fre should be connected to the primary of the coils, although most of the coils could be quency transformers ('Pl and T2). first tuning unit by throwing the switch operated without the adjustment. When (Sw) in the opposite direction. The ad- experimenting with the set, a 199 tube was in TESTING AND OPERATING justment of the oscillation control (PIH) tried the radio -frequency stage and was is not difficult. ' l'une in a station near the found to be easier to control than a 201A After the wiring is completer the set lower end of the condenser scale, turn back but, since it was not difficult to adjust the may be tested. it is best to throw the the dial of C3 and then slowly turn the dial 201A and since the signals were louder with double-pole switch so that the aerial and on the oscillation control (PH) to the left. this tube, it was finally chosen. In changing ground are connected to the primary of the On returning the dials Cl and C2 no squeals the tubes, the automatic filament controls second tuning unit, in order to get accus- should be heard; if they are heard, turn (11.2, It3, I14 and R5) were found very con- tomed to tuning the regenerative part of the oscillation control still farther to the venient, since they are easily changed, per- the receiver. It will be noticed that the l 'ft. If it is found impossible to control the mitting the use of any type of tibc without set is very selective on the short waves; oscillation in this manner, move the primary changing the batteries.

L.S. + POWER POWER

This pictorial wiring diagram indicates the exact arrange- holes, which are similarly marked in the diagram of the ment of all wiring under the sub -base panel. Letters and wiring above the sub -base panel and the leads to panel numbers in this drawing refer to corresponding wires and apparatus, which appears on the opposite page.

www.americanradiohistory.com Radio Ncws for April, 1928

www.americanradiohistory.com 1130 Radio News for April, 1928

4. a a 4'

3 DRILL HOLES Fa",- DIA. 2 4 9 SCREW . ,

v ÿN z 6' 4!y t 6 tp - l -

2,4" This drilling layout shows the exact location of all holes req aired for mounting parts on the front panel of the receiver.

In the audio- frequency stages, care should cast band, it was not unusual to find a sta- company this article, clearly show how vari- be taken to secure the proper "C" and "B" tion at almost every degree on the tuning ous coils may be plugged in the coil sockets battery voltages recommended by the manu- dials. in order to receive stations on different facturer. 'Iahis information will be found in wave bands. For receiving stations on any DATA the cartons in which the tubes are sold. COIL particular wave band two coils of identical When using two 111 -type tubes in push-pull, The illustrations of the receiver, which ac- construction are required. One coil (L1) is it is possible to secure used as an antenna Glance -hall volume. coupler, and the other Using the 210 -type (I.2) as a radio -fre- tubes with 425 volts quency transformer, on the plate, terrific Each coil consists of volume can be ob- two windings, a sec- tained. ondary (S) and a The grid condenser tickler (T). The pri- (C4) has a capacity mary winding (P) of .00025 -mf., and the has the same number grid leak (lì1) has n of turns for all wave- resistance of 5 meg- lengths and is at- ohms. Grid leaks of tached to the coil different values should socket with a hinge, be tried, in order to which makes it pos- determine which pro- sible to adjust the duces the best results. coupling between the If the set has a tend- primary and second- ency to howl, try a. ary coils. The tickler grid condenser of windings of the coils .0001 -af. capacity. for position 1.1 are In testing the re- not used. If manu- ceiver in the 11Amo factured inductors are NEWS Laboratories, C I purchased, the tickler coils covering all the connections may be wave -lengths from 10 disregarded. If the to 550 meters were used. Amateur short- coils are made at home the tickler may be wave stations from great distances were Above is shown the arrangement of omitted altogether. tuned in, and some very interesting phone parts and wiring under the sub -base In one of the drawings complete details conversation between amateurs on the Pa- panel. R1 -C4, grid condenser and leak; will be found for making the various coils cific coast was heard on the Atlantic RFC., R.F. choke coil; SW, D.P. D.T. which are required for receiving stations seaboard with sufficient volume to oper- switch. ate a loud speaker. On the regular broad- (Continued on page 1174)

10 ;' r^q - m a jI_w° - M M4m $ rl INN 3{h 444 _4_141 b I I" 61" f-{ -t- l' 1 - 2t "I r 22 HOLES COUNTERSUNK. -6-SCREW HOLES 32' +WIRE HOLES 3s +A" SCREW & The panel layout showing location of holes required for mounting parts on sub -base nanel.

www.americanradiohistory.com Radio News for April, 1928 1131 A Novel Automatic Volume Control The Amplification of the Radio- Frequency Tubes is Controlled by the Output of a Two -Element Rectifier, Which Replaces the Usual Detector

By Harold A. Wheeler

IN the present radio receiving sets em- frequency components of the pulsating recti- Fig. 1 shows the essential circuit details ploying high amplification, it is neces- fied voltage. (3) A manual volume control pertaining to the control system. 'l'he direct sary to adjust carefully a "volume con- component of the rectified voltage, free of trol" in order to reproduce signals of audio -frequency variations, is applied to the different intensities with the same audible grids of the first three tubes. If the radio - article the principle intensity from the loud speaker. There are THIS explains frequency- rectifier voltage could exceed a of a most ingenious device by various devices which could be employed to value of about ten volts, this automatic grid which it is possible to stake a radio set regulate automatically the amplification of bias would thereby cut off the signal through adjust itself to the fluctuations in the the signal, sonic of which employ moving the radio -frequency amplifier; so the recti- strength of the received signal, thus mechanical parts. It is the purpose of this fier voltage cannot exceed this value. partially overcoming fading, etc. This paper to describe a simple electric circuit, is brought about through the use of a RESULTS OBTAINED without moving parts, in which the ampli- rectifier circuit, rather than the common fication is regulated automatically by the Fig. 2 shows graphically the performance amplifying detector; and employing the signal, and the loud- speaker intensity of the radio-frequency amplifier with and variations in the rectifier output to vary reaches approximately the desired level for without the automatic control. With the the voltage on the grids of the R.P. each signal, independent of the signal inten- system described, the rectifier voltage and tubes, and thereby their amplification. sity and therefore irrespective of a rea- audio -frequency voltages are nearly inde- While the system, owing to the many sonable amount of fading. pendent of the antenna voltage, when the problems yet to be solved in its opera - latter exceeds the threshold value. The Any device to accomplish this object with- tion ,muter present -day broadcast con- curves I, 2 and 3 show the performance of out introducing distortion of music or ditions, is yet only in the experimental the system when the automatic grid bias speech t be operated by the signal -car- stage and further data are not available is applied to one, two, or three tubes, re- rier wave. Any variations in this wave's for publication, it is very interesting spectively, of the radio -frequency amplifier. intensity must be compensated by reciprocal and will afford the more inquiring con- The degree to which the signal can be cut variations in its amplification. 'l'he method structor an opportunity to study a very off in one tube is limited by two factors. be described provides for controlling the to novel circuit action. -EDITOR. First, any error in neutralizing the grid - anti diner, thereby main- radio- frequency plate capacity permits signal current to pass taining the desired signal level in the do tector or rectifier, audio-frequency amplifier RECTIFIER speaker. and loud Fig. I: This schematic TUNED NEUTRALIZED R.F. AMPLIFIER AND FILTERS A.EAMPLIFIER diagram shows the fundamental circuit ar- VOLUME ESSENTIALS OF THE CIRCUIT rangement of the au- .000tmf. ¡meg.0lmf.";CONTROL tomatic volume con- TO TO trol. Only the first . A set which has been constructed for REST . REST R.F. stage appears OF OF broadcast reception, embodying this auto- here, but in the others R.F. A.F matic volume control, comprises the follow- 2 -me go h In resistors AMP AMP 'el would be connected be- ing component sections: (1) A four -stage tween their grid cir- radio- frequency amplifier of the well -known cuits also and the rec- tifier output. This cir- cuit is still in the ex- perimental stage, and has not reached a rom- mercial basis; other circuit constants, there- fore, are not available at the present time. FIG. I. -..-WITHOUT_ CONTROL through the tube, even when its mutual con- ductance is zero. Secondly, the sharp bend °CUT -OFF° RECTIFIER VOLTAGE in the plate- current -grid- voltage curve causes distortion of a strong signal on the Fig. 2: These curves sl:c grid, when the mutual conductance is re- the performance of the by bias. view of R.F. amplifier with and duced too far the grid In II without the automatic vol- such limitations, it is undesirable to reduce ume control. It will be per stage below about seen flue roiti, three tubes the amplification ratio (curve III) the regulation 1/10 of its normal value. \l'hcn controlling -WITH AUTOMATIC CONTROL is much more uniform these become un- than with two tubes (curve several tubes, limitations II) or with one tube important. The Last radio-frequency stage (curve I). ¡THRESHOLD' ANTENNA VOLTAGE is not controlled because it must supply as high as ten volts to the rectifier. R.F. ANTENNA VOLTAGE DISTORTION AVOIDED FIG. 2. The properties of the two -element rectifier contribute largely to the simplicity of the neutrodyne type, with UX -201A tubes, the in the form of a voltage -attenuator con- control system. Fig. 3 shows the nearly antenna circuit tuned by one dial and the nected to the grid of the first audio -fre- linear proportionality between alternating four coupling transformers tuned simultane- quency amplifier tube. (4) A four -stage and rectified voltages in this form of recti- ously by a second dial. The total amplifica- audio- frequency amplifier and loud speaker. fier, as contrasted with the irregular per- tion is controlled by varying the negative The entire set, except the last two audio - formance of the three -element detector. 'l'he grid potential of the first three tubes. (2) frequency stages, is enclosed in a grounded signal modulation is rectified without dis- A two- clement rectifier with simple filter metal box divided into compartments, one tortion. Also the average rectified voltage circuits to reject the radio- frequency cur- for each tube with its preceding coupling is equal to the carrier voltage rectified; rents and to segregate the direct and audio- circuit. (Continued on page 1156)

www.americanradiohistory.com 1132 Radio News for April, 1928 A Really Portable Radio Set

An Efficient Little One -Tube Receiver, Which Weighs Less Than Four Pounds and Can Be Slipped Into an Automobile Side Pocket, Is Easily Made of Old Parts

By J. B. Armstrong

(1 of the so-called "portable" The metal case for this receiver measures radio1' receivers which the writer 7 x li,'k x 3 5/16 inches and is made of alu- has seen are portable in about minum 1/16-inch thick. The long sides are M the same sense that a steamer flanged over and screwed to the ends, and It is evident from trunk is; that is, you can put a handle on the bottom is attached with angles. this illustration the latter and drag it around with you. that the portable DISPOSAL OF BATTERIES radio set described It is easy enough to compress the parts of in the accompany- a four- or fire -tube set, or even those of a Referring to the sketches of the set, A ing article is realy portable. The superheterodyne, into a box about the size and B are the "A" and "B" batteries, which whole instrument of a lady's overnight bag; but, after you've are used to operate a UX -199 tube fitted weighs less than half a dozen cells four pounds and installed dry and at least into the UX socket shown at D. The "A" can be easily car- two "B" battery blocks and attempted to battery consists of two of the larger unit ried with one hand. carry the outfit a few blocks, you will lose cells used for flashlights; these are con- your enthusiasm for portable radio and drop nected in series and held in a special com- into the nearest drug store for a bottle of partment composed of two bakelite end muscle liniment. pieces separated by two sides of aluminum. the cells to be connected in series with a The writer has designed a portable radio This compartment is fastened to the case strip of bronze screwed to the bakelite end receiver which is really portable in that it by machine screws going into one bakelite piece on the side of the box. These bake- can be carried in one hand and will not endpiece, as shown in the sketch at point lite end pieces should have a groove running cause drooping of the shoulders. It weighs X, top view. The lower cell goes into the from top to bottom, to leave room for the less than four pounds, complete with bat- compartment with the " +" terminal towards brass ferrule of the terminal to slide into teries; so a description of it will undoubt- the side of the box to which the compart- the compartment. The series bronze strip edly be of interest at this time of the year, ment is fastened. The upper cell goes in is screwed into the groove in the bakelite with Spring not so far away, and the call with the " +" terminal facing the other way. on the box side; this is clone in order to of the open faintly audible in the distance. This arrangement is used in order to allow allow the " +" and "-" terminals of the battery compartment to come out conveni- ently for wiring. The bronze connector is bent outwards from the bakelite to make contact with the lower cell's " +" terminal -,,_; and the upper cell's " -" case. Two separate ; ',,,.= clips are screwed to the other bakelite strip : A.1; ' - , ' - '1`1;4/...1E.--. of the compartment to form the " +" and I I " the battery compartment. ' terminals of - _.:. q ! H" -" ' 'DIAL The "B" battery consists of a single 221/2- 1 Í, K= r; 1 WINDO' volt block of the smallest size. It goes into _.'- 1 --i-_:.a _ ia I ! Ì the box upside down and connects with M- I r'--- ; -T O1 bronze clips screwed to a block of wood M, -- ill.'"Meow fastened to the bottom of the box with wood V I EV I IIIIi e ol ® -_ - screws. If these clips R, are bent, U- : _ I shaped, the lower side of the U can be used G-- ^ , ; tpN:`, as a lug to which is soldered a connection _. ,! i' ., ;; os as shown in the sketch, side view. The , ' wooden block is made to fit close between D-- i ÍIIr e = }i = the "B" terminals so _ ...... _.. . battery that, because 'Pi -1 I of the difference in spacing of the terminals from the edge of the battery, it can be con- I F D-. nected in only one way; insuring correct / N L r- polarity. \ = á r PLACEMENT OF PARTS ®.l -, The grid condenser, of .00025 -mf. capacity, :a_. ; /K" ,; is shown G; is ;, at it screwed to the side of ' ; .- box MI& I I the before the bottom of the box is r Ì _. -SIDE attached. - II , ' ,_- VIEW -. A .001 -mf. fixed condenser F is screwed ! /t t to the bottom of the box and used as a " J ; ; ,, radio-frequency by -pass condenser. :c_J / A The variable condenser, C, is of .00035 - B mf. capacity; any condenser of this size may : '/fii`,; =° 'i.,..,,.. be used providing its spread will not exceed the depth of the box when it is rotated. G R R " .F- The condenser is secured by small brass i C angles, four in number, which are fastened The tzeo clips marked R (sicle view) make contact with the binding posts on the "B" to it by using longer assembly screws. The battery block. The 199 tube fits in the socket D, occupying the corner formed by the frame and rotary plates Inning are thus connected coil O and the `B" battery B. The other symbols in these drawings correspond to the box and so to ground and "A +" and with those in the illustration and diaprant on the opposite page. "B -". The condenser is controlled by the

www.americanradiohistory.com Radio News for April, 1928 1133 knurled disc H of 1/16-inch aluminum, condenser end of the box and insulated with around this difficulty, there should be which projects through a slot in the lid of fiber bushings and washers, with the ex- mounted within the set (under the variable the box. To allow it to project only through ception of the ground post, which is mounted condenser) an old headphone coil, of ap- the lid, the center line of the shaft of the right on the aluminum case without insula- proximately 500 ohms resistance, which condenser must be above the half -way line tion. Two of these posts arc connected to should be connected in series with the "11-f-" of the box by an amount equal to the dis- aerial and ground respectively, the other battery circuit. This will limit the short - tance the (lise projects. No clearance need two being phone connections in the plate circuited current to a harmless value, yet be allowed, between the frame of the con- circuit of the tube. This brings one pest not impair the operation of the set. denser and the "A" battery compartment, at 221/2 volts above ground with the tube if the condenser is fitted with countersunk filament also grounded; so that the tube ACCESSORIES screws bearing parts are assembly and the A handle, such as that supplied for a as shown. sawed off flush with the frame hand bag or small suit -case, was procured A be borrowed from some paper dial can from a leather -goods store and fastened to old vernier dial and cemented to the alu- the box with small metal clips, as shown; minum disc with household cement or col- the set complete with batteries weighs 3 lodion. 'l'he figures on the dial are read pounds 91/2 ounces. It is completely shielded box, through a window in the side of the and may be handled while tuning in sta- under the handle. tions without the slightest body- capacity switch L, which is mounted A filament effect. It has brought in broadcasting over on a brass plate, consists of a brass sliding distances of 1500 miles on a good antenna which slips be- member with a cross bar during the summer months. A single -turn neath two small spring -bronze strips, one loop 24 inches in diameter works excellently of which is grounded to the supporting with this little receiver; it is connected plate. The other strip is screwed to a piece across the primary coil as with a regular of bakclite and so insulated from the base. m.VGY been heard brass antenna. Station has The sliding member slides through two very clearly with this type of antenna and bridges milled to and is bent over at lit receiver over a distance of twenty -five miles; right angles on the top to provide a grip. at a distance of six miles, it comes in loudly The switch is "on" when pulled out, and enough on an outdoor aerial to be heard can he Houle flush when "off;" although aCPOSS the room on a loud speaker without opening the box The this necessitates to turn the complete wiring diagram of the portable amplifiers. Carrying the set with one hand tube on. This filament switch is the only receiver. The extra phone roil prevents dam- age to the tube filament, in rase of os acci- and using a loop consisting of three feet control used on the tube filament; as the two dental shorriren it. of wire laid across the shoulders and hang- unit cells give the proper voltage without ing vertically. one may hear broadcasting the use of a should be dis- rbeaslat, and would be horned out in case the post should from R'GY while walking about insane when -if carded the tube will no longer func- be accidentally connected to the box, as enough about radio to try it. (Yes, the tion. This will be usually after approxi- when inserting the phone tips, etc. To get writer has tried it.) mately one hundred hours of service.

TIIE CIRCUIT Now we come to the tuner; this consists of three coils, used in the conventional re- generative circuits as primary- l', secondary O, and tickler .1. The secondary, O, was wound first, using as a form, au cardboard tube such as conies around the large unit flashlight cells; it consists of a two -layer banked winding of No. 28 enameled cotton - covered wire, Ito inches long, and held in place by celluloid cement. No taps were brought out, as the tuner was found to cover the broadcast band nicely, with the .00035 -mf. condenser. (Editor's Note: Ordinarily it is against the policy of It-Àmo Ni:ws to publish hook- ups or descriptions of plain regenerative lcerirers, because of their obnox prop- erty of causing interference in neighboring sets. This portable receiver is excepted from the ban, as it is unlikely to be used in crowded districts.) 'l'he primary, which is wound directly over the secondary on the filament end, which is nearest the tickler coil, consists of three turns of No. 22 D.C.C. and is unturned. The tickler coil consists of a winding 7 /1(1 -inch long, of No. 28 S.C.C. wire in two layers (not banked, simply one over and then back on the first later) on a bakclite tube % -inch in diameter. Two pig-tails covered with soft steering are brought out from the coil of stranded wire. To rotate the tickler, the disc N, of 1/16 -inch alu- minunu, is used with a tight- jointed brass angle support Q, which is clamped at K to the dise shaft and screwed to a bakclite end piece cemented into the coil form. The control dise has bearings in a U- shaped brass strip fastened to the bottom of the box. The shaft has a shoulder turned on each end, to keep it from sliding out of the bearings; and the hearing strip itself is A view of the portable set with the corer opened. H and N are the dials which con- split and sprung to take up all play. trol the tuning condenser C and tickler coil .1, respectively. F, by -pass condenser; A, Four binding posts are mounted on the filament batteries; L, filament switch; O, secondary coil; D, tube socket.

www.americanradiohistory.com Radio News for April, 1928 What Constitutes Tone Quality? Part II of an Article in Which is Considered Sound Reproduction and its Relation to the Reception of Radio Broadcast Signals By Robert Neil Auble

IT was pointed out in the first part of CHARACTERISTICS" speaker are reached. Obviously, there is this a rticle, which appeared in March possibility of change of quality- "distor- It has been shown by various investigators RADIO NEWS, that a radio set may be re- tion" -at every point: any imperfection in garded as perfect only when the sound re- that no reproducing instrument yet devised the microphone, any fault in the amplifying produced at the loud speaker is faithfully is capable of amplifying with equal efficiency and modulating systems at the broadcast like that originally produced before the mi- all the possible frequencies within the range station, any atmospheric disturbances be- crophone. This involves the problem of in- of hearing. The amplification curves of even tween the transmitting aerial and the re- suring that every fundamental tone and the best horns, for example, show very great ceiving aerial, any faults in the tuning cir- every overtone sounded before the micro- cuit, the detector circuit, or in the audio - phone may be reproduced at the loud 16 ft frequency amplifier of the receiver -all of speaker, with emphasis unchanged and with- --142/eft these will modify the wave form of the elec- out the intrusion of any other sound what- 13%s ft ------trical energy delivered to the loud speaker ever. Y3 ft 12 ft and introduce changes in the sound waves While it is no doubt true that the rela- into which the electrical energy is converted .9%ft tive emphasis of the various partial tunes Bs/sft-- by the loud- speaker unit. must be preserved in the ideal transmitting We do not intend to go into any extended system, it is also possible, however, that a discussion of the electrical factors enumer- transmitting system may fall somewhat short ated above, since the whole science of of this ideal without objectionable results. radio design is involved. It will be suf- Certain types of extraneous sounds must ap- ficient here to state that almost any well - parently be always present in any sound - designed radio set now on the market, if reproducing system-as needle noises in the properly handled, will deliver to the loud noises on the telephone, phonograph, line Pi speaker electrical energy whose wave form static and other background noises on the Fiy.B M,I! UNIT is practically identical with that which left radio. Still, it is obvious that, in amplify- the antenna of the broadcasting station. A series of resonance Pipes of the above pen. ing radio speech and music above the gen- eral dimensions world reproduce tones for eral noise level, the idea will be to amplify which they were especially designed, but no DISTORTION IN THE SPEAKER others, with full efficiency. all the partial tones to the saute degree. Loud -speaker design has not, however, Certainly no radio set designed up to this irregularities. Horns usually amplify the kept pace with the design of other radio finie may be regarded as perfect in this units. As was mentioned above, most of respect. upper ranges of frequencies more or less satisfactorily, but give only selective ampli- the horn -type speakers amplify the higher So many factors are involved, and so partials well enough, but do not handle the many difficulties are encountered, that it is fication to the lower frequencies. Cones amplify the lower frequencies more effi- low notes efficiently. And without the sup- nothing short of miraculous that radio port of the strong bass notes, the principal speech and music are so deceptively like the ciently, but fail usually to handle the upper tones so well. charm of music is lost. The writer has fre- originals. Very fortunate it is that so few quently heard through radio receivers or- of us have ears so delicately attuned to To simplify the discussion of quality, it is desirable to remember that the transmitting chestral arrangements which seemed pitched sounds that we are able to find any fault a full octave higher than the musical score at all. unit is essentially a device to convert the energy of sounds produced before the mi- indicates. The horn was failing to deliver crophone into electrical energy; and that it any of the fundamental notes, leaving the is with electrical energy with which we are listener to depend entirely upon the over- concerned until the coil windings of the loud tones. Such loud speakers are especially cruel to the voices of male speakers, whose voices are robbed of the sonorous tones of the lower register which give them their character and identity. On the other hand, the cone and drum types of loud speakers so emphasize the lower tones that speech and music acquire a disagreeable rumbling character, resem- bling the sound of thumping on an empty barrel. A horn is essentially a resonance cham- ber which amplifies the sound of the loud - speaker diaphragm, by virtue of the fact that the air column confined within the horn is forced into vibration in unison with the diaphragma. If the horn were cylindrical In shape, it would respond only to sounds whose wavelengths are twice the length of the tube, or to sounds whose wavelengths are such that the tube is exactly one -third, one -fourth, one -fifth of them, and so on. For example, if the tube is approximately 27 inches long it will respond to middle C Two types of modern load speakers. The exponential horn at the left has a chamber (256 vibrations per second), to C' ( =512), approximately nine feet long, with an opening 18 x 24 inches. The cone -type speaker at to G' ( =T68), etc. The intermediate tones the right is 24 inches in diameter and ins five points of suspension. tare not amplified. Since a cylindrical reso-

www.americanradiohistory.com Radio News for April, 1928 1:35 nance tube responds only to selected sounds, of size to the dimensions of the cabinets with those of the horn. The writer de- to reproduce the whole range of audible in which they are to be placed, cannot re- scribed one possible scheme for accomplish- sounds with cylindrical resonators would spond to the lower notes adequately. Music ing this result (Ramo NEws, October, require a series of resonance pipes like a heard through such horns lacks depth and 1927), by means of an ordinary loud -speaker concert pipe organ. Such a "loud speaker" character. 'l'he melody and harmony may unit, so arranged that the diaphragm actu- would, of course, be out of the question in be ever so brilliant but, without the back- ates the drive-rod of a cone on its lower the average residence. A sketch diagram of ground of the bass notes, the final product surface, while the upper surface is open to a possible loud speaker of this type is given seems shallow and uninteresting. The basses the conventional horn. in Fig. 8. are like the background of mountain and A much better arrangement has been de- Such a loud -speaking unit as represented forest, over which the strings and wood- signed by Dr. A. L. Foley, of Indiana Uni- tones winds play with all the gorgeousness of a would efficiently amplify only the versity (Proceedings of The Indiana Acad- beautiful sunset. emy of Science, 1926, p. 131). Dr. Foley W V constructs a horn of massive clastic mate- OF ACTION THE CONE rial, so curved and with such a rate of in- The cone type of loud speaker depends crease in its diameter that the best advan- upon another principle of sound amplifica- tages of the horn are retained. Within the tion. The loudness of a sound, at a given horn, and forming one wall of the air pas- distance from its source, may be increased sage, is placed a sounding board of thin by increasing the amplitude of the vibration clastic material (see Fig. 9). The sounding (increasing the actuating forces), or by in- board preserves the amplification ratio for creasing the arca of the vibrating object. the lower notes, while the horn amplifies the The cone accomplishes its purpose by substi- upper notes, as explained above. Dr. Foley tuting its larger surface for the solidi dia- describes the action of his horn, as follows: phragm, which is the source of sounds in "The cross -sectional area of the passage the horn type speaker. of P being relatively small, the sound waves Such a large vibrating surface disturbs a (compressions and rarefactions of the en- much larger volume of air than is possible closed air) tend strongly to produce vibra- 4 crosascctio al viewview of a sound-amplifying with the diaphragm, so that the amount of tions of the walls of the passage. 'l'he horn designed by A. I. Foley, of Indiana two University. energy reaching the ear is increased with- side walls W and the lower wall L are mas- out the use of amplifying horns. The ma- sive and stiff. The upper wall, called the which are harmonics (even multiples) of the terial of the cone must vibrate in numerous vibrator, V, is of thin elastic material and major scale (without the "semitones") be- irregular segments if it is to amplify all the is of sudi a shape that it can readily vi- ginning with C e 32 vibrations per second. elements of the complex tones. The cone is brate in unison with the sound waves pass- This would include most of the notes ordi- a modified Chladni plate, such as was de- ing underneath. The vibration of V sets up scribed 1. narily used in music, but even so, would not in Part As pointed out there, the waves which pass across the horn (trans- higher the be completely satisfactory, unless the in- frequency of the note sounded, verse to the horn's axis), where they are the be struments at the broadcast studio were smaller must the vibrating segment. again transversely reflected by the top '1' tuned to physical pitch and unless the tem- Since the factors of texture and elasticity to the vibrator board. Several such reflec- perature in the studio were the same as in establish a limit to which the segments may tions may take plaice before the waves finally reduced, the room containing the speaker. Under be such a vibrating cone cannot emerge at B. This multiple reflection again such conditions the device would be highly amplify sounds whose frequencies pass' a greatly increases the effective length of the efficient. fixed upper limit, if it is at the sane time horn and increases the frequency range of to amplify the bass notes, for which it is resonance. especially suitable. 'l'he absence of the up- THE "EXPONENTIAL" HORN "Note the end per partials in sound reproduced by a cone that wider of the vibrator Fortunately, however, the effect of a mul- is at the rear end of U and that it naturally may be se- gives it the peculiar "empty- barrel" effect. tiple series of resonance pipes vibrates at a louver rate than the narrow cured by gradually increasing the diameter It is now evident that it would be desir- of the tube from its mouth outward toward able to combine the advantages of the cone (Continued out page 1179) the bell. If such a born is used the sound waves are internally reflected so that the tube becomes less and less selective; i.e., it becomes resonant for an increasingly large number of tones, the fundamental tone, how- ever, remaining the saline as that of an open cylindrical tube of the same length. A sim- ple straight "conoidal" horn haying a loga- rit5rnic rate of increase in its diameter from vertex to bell, will respond to practically alt the audible frequencies; prodded its length is of the order of twenty -live to thirty feet. A horn of such length would be unwieldy, and despite its superiority over every other type of amplifying horn, must give way to less cumbersome, though less perfect horns in the average home. If a horn, such as described above, be curved more or less abruptly the number of internal reflections is increased, making it possible to reduce the length without di- minishing the number of frequencies to which it will respond. There is, however, a considerable loss of energy at such points of curvature, unless the amount of curvature at each point be exact. The superiority of certain horns now on the market is prin- cipally due to a better calculation of the curvatures. But no matter how perfectly the curva- tures are calculated, there is a lower limit to which the length of a horn, measured along its axis, may be reduced. So many A gigantic exponential horn made in 1922 for the purpose of studying sound zeo; , . in horns, answering the demand for reduction this type of horn. It is capable of amplifying the lowest audible tones.

www.americanradiohistory.com 113u Radio News for April, 1928 Controlling Volume in Your Receiver

An Explanation of the Respective Merits of the Methods of Controlling Receiver Volume by Means of Variable Resistors

By John B. Brennan Jr.

THE method by which volume is to be (C) The filament rheostat. no coil pick -up, or unless the receiver is be- controlled in a radio receiver de- (D) A variable resistor in series with the ing operated at a point sufficiently distant serves a considerable amount of at- "B -j-." lead to the R.F. tubes. from the nearest broadcast transmitter so tention. When listening to a local (E) A variable resistor across a tuned that there is negligible pick -up by the coils. station it will be usually found necessary to circuit. You can determine whether this effect will utilize this control on the receiver to reduce Method A, utilizing a variable resistor of be bothersome by disconnecting aerial and the signal somewhat, so that the reproduced about 200,000 ohms connected across the an- ground and tuning the set to receive the sta- program will not be too loud. Therefore, tenna coil, is generally quite satisfactory. tion whose signals are normally the loudest. the method used should be one which will regulate the volume without affecting the performance of the receiver in any way. P. F. TRANSFORh ERS We may define the ideal volume control as one which will control the volume output of a receiver without affecting in any man- O ner the receiver's selectivity or fidelity of ó reproduction. Few of the methods usually O adopted measure up to this standard; but T e there are several which are quite satisfac- tory. In the following paragraphs we will indicate the characteristics of the various types; so that the reader will be able to de- termine, by examining his receiver, whether that employed is really the most satisfactory one. To make our discussion systematic, we BP will begin by dividing volume controls into O two broad classes, according to their posi- tions in the circuit. The first group will in- .b + "A' - "a+asv "B +90 v. FIG. 1 clude all the methods whereby the volume is controlled by some device in the radio- frequency circuit. The second group in- Five different methods of controlling the volume are indicated by letters in this cludes all controls that function in the diagram of an R.F. amplifier and non -regenerative detector. audio-frequency circuits. sig- METHODS IN THE R.F. However, if the receiver is unshielded and Ululer these conditions a good healthy is being operated close to one or more nal indicates that there is coil pick -up, and In Fig. 1 is shown a conventional circuit volume- control method A should not be consisting of two stages of tuned- radio- broadcast stations, it is possible that the coils themselves will pick up quite some en- used. frequency amplification, followed by a non- regenerative detector. In this single circuit ergy; and therefore the output of the re- A resistor in series with one of the tuned we have indicated five volume controls, as ceiver will not be zero even when the volume circuits, as indicated at B in Fig. 1, is fre- follows: control is set for zero resistance. This is a quently an effective means of controlling distinct disadvantage, for the control is not volume where the selectivity problem is not (A) A variable resistor across the pri- effective on those stations (powerful nearby severe. When resistance is introduced into mary coil (P) of the antenna coupler. locals) where it is most essential. This type ,a tuned circuit the selectivity of the circuit (B) A variable resistor in series with a of volume control is not recommended un- is seriously reduced, and it is possible that tuned circuit. less the receiver is shielded so that there is interference will be experienced between stations operating on adjacent channels. TRANSFORMERS REGULATING "A" AND "B" VOLTAGES A rheostat controlling the R.F. tube fila- a ments (C, Fig. 1) is frequently used as a volume control and really proves very satis- o factory, except, of course, with A.C. -fila- ment tubes. As the filament current is re- duced, the emission from the filament is de- creased and the resultant increase in the plate impedance of the tube causes the amplification to decrease; the signal finally reaching the detector is thereby reduced. It is a good idea, when such a control is used, to place a fixed filament resistor R (Fig. 1) in series with the volume- control rheostat. This resistor protects the tubes from an o O o o O O O overload - + - "A + - of filament voltage for then, even "C" "B" FIG. 2 with the rheostat resistance all out, the fila- ment voltage is limited to the correct value Three methods of volume control in a transformer- coupled audio- frequency for the tube. amplifier are shown at F', G and H. Since this control functions by limiting

www.americanradiohistory.com Radio News for April, 1928

TABLE OF RECOMMENDED RESISTANCE VALUES FOR VOLUME CONTROLS sistance across the secondary of a tn. a lower resis. Average Value in former being equivalent to See Fig. Position of Resistor Ohms (Maximum) Characteristics ance across the primary. The method used (1 A) Across antenna coil 200,000 Very good, except for an unshielded receiver in a congested broadcast area. is optional, the major difference being that (I B) In tuned R. F. circuit 400 Decreases selectivity. a variable resistor across the primary for 1 C) Filament rheosht t Very good. with most types of receiver. volume control should have a maximum 1 D) In series with R. F. B +" lead 200,000 Satisfactory I E) Across tuned R. F. circuit 200,000 Decreases selectivity. value of about 100,000 ohms, and a resistor 2 F) Across A. F. T. primary 100,000 across the secondary should have a value of (2 G) Across A. F. T. secondary 500,000 These methods are generally less satisfactory, as (3 A) *Potentiometer -grid leak 500,000 they permit the detector and A. F. amplifier to about 500,000 ohms. Method H is not satis- 1 with consequent (3 B) *Variable grid leak 000.000 be overloaded by strong signals, factory, except in special cases; as, for ex- (2 H) Across loud speaker 25.000 distortion. *In resistance -capacity-coupled A. F. amplifier. (Depends on number and types of tubes. ample, when the receiver is located some distance from the loud speaker. lite emission current, thereby increasing the IN A.F. CIRCUITS Volume control in a resistance- or im- plate impedance of the tube, it follows that pedance-coupled amplifier can easily be ac- it must produce some distortion. By experi- We now come to the method of controlling complished by using a high -resistance po- ence, however, we know that the distortion the volume by means of some adjustment in tentiometer (Fig. 3, A) or by simply using created is not generally noticeable and the the audio amplifier of a receiver. First, let a variable high resistor for the grid leak method can therefore be considered a good one. At D in Fig. 1 we have indicated another volume control arrangement which functions bv lowering the amplification in the ILK aunplifìcr through a reduction of the plate voltage. When this type of control is used, It by -pass condenser (lie') should always be connected from the "A -" to that side of the variable resistor or leading to the pri- mary of the 11F. transformer. The con- denser should have a value of .005 -mf. or more. Method E, utilizing a variable resistor across a tuned circuit, falls into the same class as method B. A resistance of given value across a tuned circuit is equivalent to a smaller resistance connected in series with 0'O D o 0 o o 0 o the tuned circuit. Methods B and E there- - A- + - FIG. 3 fore fall heir to the same objections and neither of them can be considered a really Tuyo output volume of a. resistance- coupled amplifier. of volume control. This wags of controlling the satisfactory method A2-potentiometer-type grid leak. straight variable grid leaks. completes our story on volume controls B- functioning in the R.F. portion of a re- ceiver. The various controls listed are us consider a two- stage, transformer- coupled (Fig. 3, B). The method indicated at A is grouped in the table; you will find listed amplifier (see Fig. 2). Here we have indi- somewhat preferable if a high- resistance po- there the major facts concerning each cated three controls, F, G and H. Methods tentiometer with a resistance value from method. F and G are really similar; a very high re- (Continued on page 1158) How Powerful a Tube Does Your Set Need?

IS exceedingly high plate voltage necessary USE OF SMALLER TUBES stilts, particularly in the case of the high - for high quality in radio reproduction? Now in a case like this, where quality, voltage amplifier, are far from satisfactory. Many set owners, noticing the numerous rather than quality plus tremendous volumt, In the case of sharply -tuned receivers, seri- constructional articles dealing with "B" is the primary consideration, there is noth- ous distortion results from the suppression power devices having an output of 500 or ing to he gained by the use of very high of the side bands when the set is detuned; more volts, and designed for use with power power. To be enjoyable, the device of while extraneous noises, static, line disturb- tubes of the 210 type, are perhaps inclined very high voltage would of necessity have to ances, etc., are amplified out of all propor- to believe that real quality can only be ob- be operated at a point considerably under tion to the signal. tained through the use of these voltages maximum output. If a proper means of 'VOLUME OF QUALITY and tithes. controlling this volume . were used, the 'Phis, however, is not always the case. A quality would not suffer; but it would not In the last analysis, quality in the re- moderately powered amplifier, using tubes he better than the maximum output of an produced signal is not so much a matter of of the 119 or 171 type with plates supplied amplifier more in accordance with the tastes volume as of freedom. front overloading. from a 150 - or 180 -volt source, can, in most of the average set owner and the acoustical Were it purely a matter of amplification, circumstances, give results that will satisfy capacity of his home. tubes of the 201A type, or the "high nul" the most critical. The main advantage Of course, there is no denying the fact tubes, would be far superior to those of to be expe('tc(I through the use of higher that power and fidelity in reproduction arc, the 171 and 210 types. The superiority of power is a. gain in volume and the increased up to certain points, closely associated. The the power tube lies, not in its ability to realism that conies in having, let us say, the set owner should remember, however, that amplify, but in its ability to handle great volmne of an orchestra, as it comes from a moderately- powered amplifier puts every volume without overloading. the speaker, equal or exceeds that of the bit as much energy into the loud speaker as When, for example, a tube of the 201A orchestra itself. However, it is obvious that a very -high -voltage device operated at a type is used in the last stage of an ampli- the average set owner is not desirous of fraction of its volume. In the latter case, fier with, let us say, 90 volts on the plate, having a twenty- or sixty -piece orchestra the energy, as expressed in the A.C. varia- the sounds issuing from the loud speaker going full tilt in his or her living room. In tions of the plate current, remains in re- are apt to be thin and with the tones in the a small room -and many rooms are small serve, or is dissipated by means of the lower end of the musical scale missing. nowadays -this would be unpleasant, even volume control. When control is attempted Now, as we increase the plate voltage, the painful. Therefore, an amplifier capable of by means of reducing the filament voltage, quality of reproduction improves until a giving this volume could seldom be used. or through slightly detuning the set, the re- (Continued on page 1101)

www.americanradiohistory.com Radio News for April, 1928 The Action of "B" Socket- Power Devices An Explanation and Discussion of the Necessary Components of Such Apparatus, and the Types of Each Most Desirable By Herndon Green

IF an investigation were made, of the then it is usually not of sufficient voltage "C" battery is employed. To obtain both the various steps which have been taken to be useful as a "B "- battery substitute. "B" and "C" voltages from a "B" power - in the progress and development of Alternating current is decidedly cheaper to supply device is not difficult; yet immedi- radio receiving sets, an interesting story distribute than direct; but with alternating ately we see that at the output of the de- would unfold itself. Even our now-com- current we encounter a number of condi- vice at least 220 volts are required. Since monplace "B" battery has behind it some tions which make its ultimate use for power- this is just double the value of the line or interesting history which, to the majority of ing a receiver somewhat complicated. house voltage, a transformer unit is em- broadcast listeners, is unknown. The voltage that is supplied to the plates ployed to "step up" this line voltage. En- Toward the end of the crystal -detector of radio vacuiun tubes must be of a direct - gineers can, by calculation, determine the era, when attention was turning to the de current nature, be steady in value, and free electrical and physical dimensions of a Forest bulb and the audiotron, there was no of pulsations that produce hum. Alternat- transformer that will step up the line volt- such unit as a 22 %- or a 45 -volt "B" bat- age to a predetermined value. Now, one tery. A set -builder who was so bold as to step of progress has been made toward the employ one of these new -fangled tubes re- ultimate goal, that of changing the low - lied chiefly on a bank of 4% -volt flashlight value alternating-current to a higher value, cells for his plate supply. Today we have suitable for use as "B" supply. Yet, even quite efficient heavy-duty "B" batteries; but in its stepped -up state, the alternating cur- still the quest goes on for something in the rent is not immediately suitable for use. It line of "1,' power-supply devices with which is necessary to change the A.C. to D.C., to obtain "B" potential for the tubes in a this operation being accomplished by a "rec- radio receiver, via the light socket. tifier" unit (see Fig. 1). The last few years have seen great strides of progress in the "B" socket-power field. AUK S?JOOTHING OUT THE CURRENT In fact, the advance has been so rapid as to DISCHARGE i leave the majority of listeners -in without an Rectifiers may roughly be divided into understanding of the principles embodied In three lasses: chemical, gaseous and tlier- these devices; with the result that unscru- mionic. While they operate somewhat dif- pulous manufacturers and dealers have un- ferently, they produce the same general re- loaded on an unsuspecting public a great sults, and have the same purpose; that is, deal of worthless and useless junk labeled FI6.3 they pass current in one direction only, as "B" power-supply apparatus. It is the The action of a filter unit may be thereby changing an applied A.C. to, a aim of this article to acquaint the readers pulsating D.C. While rectifiers generally of RADIO NEWS with a simple, non -technical likened to that of a system comprising a pump, a tank and a discharge tap. take the form of one of the three types men- explanation of the function of the component tioned, it is possible that any of these three parts of a representative "B" power -supply The tank stores up the periodic charges and discharges them in a steady streams, may be of the "full-wave" or the "half - device. wave" type of rectifier. In the half -wave rectifier only half of the alternating -current THE HOUSE CURRENT ing current is usually considered as steady impulses is used, as illustrated in Fig. 2A. If our houses were powered with direct in value, not fluctuating appreciably; but it In the full -wave type of rectifier tube, the current, of say, 180 or 220 volts, there would is not of direct -current nature and it does elements are so arranged within the tube probably be no need for any more compli- produce considerable hum. Therefore, in as to utilize that half of the wave unem- cated device than a smoothing or filter de- utilizing alternating current for a "B" sub- ployed in the half -wave type of tube; with vice and a voltage divider; so that various stitute, a number of electrical changes must the result that the number of pulsations in the resulting direct current is doubled; thus lower values of voltage might be obtained in take place before it is satisfactory for Luse. addition to the voltage value of the house In the first place, the line -voltage of a making the job of "filtering" not so difficult. supply. (An assembly of similar nature house supply is usually too low for imme- Still, this pulsating direct current is not was described in RAmo NEWS for January, diate use. When a receiver employs a power ready for use. The pulsations would pro- duce a disagreeable hum in the loud 1927). However, in only a few sections of tube of the 171 variety, at least 180 -volt is the country is direct current available, and "B" potential is desirable and a 40.5-volt speaker; so it necessary to smooth them out. The unit used for this purpose is called a "filter" and consists of large choke coils and coils 30V0LT large fixed condensers. The choke TRANSFORMER RECTIFIER FiLTER VOLTAGE o- TO have the property of retarding the flow of A C .y DIVIDER ó- RADIO SET alternating or pulsating current, but quite 4 A. readily pass direct current; while the con- ü FIGI 4 r I densers act as a storage tank or reservoir, rT so that the current may build up to a usable value and not immediately dissipate itself, as would be the case if these condensers were not included in the circuit. The action PULSATING D.C. SMOOTH D.C. DIFFERENT of the filter unit very well be VOLTAGE might likened STEPPED-UP A.C. VALUES to a tank, which receives at its top a series of charges of water from a pump. The tank F I 6.2 stores up these periodic charges and then, Fig. 1 shows the various instruments for preparing the needed through an outlet at its bottom, discharges D.C. for the plates of tubes. Beneath, in Fig. 2, the changing the water in a strong, steady stream (see F1G.2A of the waves is shown, diagrammatically. Fig. 2A illustrates Fig. 3). half -wave rectification. Three of the four necessary steps have

www.americanradiohistory.com Radio Nervs for April, 1928 1139

which go to make up this very important part of the complete device. The chokes a sufficient current- carrying 'ööam--f150156' o B+M'AX. should have L1 L2. RI rating, in excess of what will ultimately be o B+A.F. drawn from the "B" device, so that at no time is its carrying peak reached. When the R2 C2 CIL C4 C B+R.E current rating of a choke is exceeded it rap- 110.31 idly decreases in inductance value, and sloes A.C. . -o B+DET not then measure up to the requirements of R3 a satisfactory choke. 5B 144 High operating -voltage rating of the filter essential successful op- LOUD- SPEAKER condensers is to the RETURN eration of a "13" power -supply device. Here again, as with every part of the device, re- C-POWER STAGE liable apparatus should be employed. A R S A.C.FILAMENT SUPPLY TO rating of 600 volts, D.C., for the condenser POWER TUBE nearest the rectifier part of the circuit is not too great, and lower operating-voltage T =LINE TRANSFORMER RI = 2000 OHMS values for this particular condenser should FI0.6 II, L2 = 30-HENRY CHOKES R2 5000 be avoided. The condensers in the re- CI =4MF. R3 =5000' -" C2= 4MF. R4 = 2000 mainder of the filter circuit may be of the C3= 6MF. R5 = .06 MEGOHH. 400 -volt IMF. rating. C4,C5= In the voltage divider, we are presented In this schematic diagram we have indicated the 'use of a ihermionic rectifier tube with the problem of selecting resistance D.C. circuit constants arc given. for concerting the A.C. to pulsating Appropriate units that are constructed in such a manner that they will not only carry the maxiuuuu current under full load but also dissipate filament amplifier now been described. That is, the original and for the of the power the heat generated by the passage of the has been tube. 11(1 -volt alternating current current through them. There are a num- a guaran- stepped-up, it has been rectified or changed The rectifier tube should have ber of types of resistor now obtainable, finally it teed life of 1,000 hours or more; it should to a pulsating direct current, and which fall generally into two classes: (1) pulsations eV ated or have the proper current rating in milliam- has bad these the wire -wound type; and (2) the carbon - ironed out by means of a filter system; leav- peres to insure its suitability for use with the compression type. non direct current other apparatus employed. A'owacbtys it is ing only pure, -pulsating In summarizing, we find that all A.C. of the correct voltage value. "B" power -supply devices can be analyzed ----o MAXIMUM as follows: first, there is a transformer DIVIDING TIIE VOLTAGES ,._.INTERMEDIATE which R3 steps up the line voltage to a value Now if only one value of "B" voltage in excess of what will ultimately be em- INT. ployed at the output (this high starting. were required by a receiver, the ,job would R É R2 end lucre; but the various tubes in a re- E voltage is necessary because of voltage <-o INT "drops" in the rectifier and filter systems): ceiver require different values. For in- RI stance, the radio - frequency amplifier tumbes secondly, there must be a rectifier, of either may require 67 or 90 volts; the detector the half- or full -wave type, which converts FI 0.S nay operate most satisfactorily at 45 or 67 FIG.4 or changes the stepped -up alternating cur- volts; the first audio amplifier many take 90 These two diagrams illustrate how dif- rent into pulsating direct current; thildly, volts and the final or power stage may re- ferent voltages are obtained from the there is a filter system which smooths nuit quire 135 or 180 volts -depending on maximum output of the rectifier. the pulsations and acts as a storage tank whether a 112 or a 171 type of tube is em- or reservoir; and fourth, there is a voltage - ployed here. Therefore, it becomes neces- possible to purchase rectifier tubes which divider system wherein the use of variable sary to utilize the maxinnuu output of the are entirely satisfactory for use in "B" or tapped resistors makes available interme- "IS" power -supply device in order to make power- supply devices and have current rat- diate values of output voltage, satisfactory possible the use of these intermediate values ings ranging from 85 milliamperes to 300 for application to the plate of the different by of voltage. This is best accomplished and 400 milliamperes; the latter type is suit- tubes in a radio receiver. means of a series fixed or variable re- of able for "A" or filament- current supply. In Figs. 6 and 7 are shown represent.,tivc sistors located in the circuit, directly across In the filter unit, caution must lue exer- "B" power-supply circuits, employing the the output terminals of the filter section. cised in choosing the condensers and chokes thermionie and gaseous types of rectifiers. It is one of the laws of electricity that, if a resistance It be placed across a source of voltage, E, as in Fig. 4, any intermediate LI L2 value of voltage (Es) can be obtained. This will vary from zero to maximum volts, de- 8+MA' pending upon the position of the movable RI contact C; it will be least this arm when B+A.F. arm is brought nearest to the negative side 1104 R2 of the output. This "potentiometer" A.C. prin- C5 ICG C7 t-o 8+R.F. ciple is applied in the "voltage -divider" units employed in "B" power -supply devices; t---o 8+DET. With the addition that, not alone one cou- R3 Inct area but as many as there are inter- B mediate voltages required are used. Usually R4 the resistance does LOUDSPEAKEF not consist of one unit RETURN but of several individual units, as shown in R5 Fig. 5. C- A.C.FILAMENT THINGS TO SI.E TO SUPPLY TO POWER TUBE To recapitulate: there are a number of re- quirements which the several units compris- T LINE TRANSFORMER C6,C7 =IMF. LI,L2= 30 -HENRY CHOKES ing a "B" power -Supply device must possess. RI = 2000 OHMS RT B5- MILLIAMPERE RECTIFIER TUBE (FULL-WAVEI R2= 5000 In the matter of the transformer, one should CI,C2 -.IMF. BUFFER CONDENSERS FIG.7 2MF. R3= 5000 be selected that is well made, mechanically, C3,C4. R4= 2000 C5' BMF. R5 .05 MEGOHM and has sufficient windings, not only for the "B" supply, but also for the rectifier tube A gaseous tube. RT, is the rectifier used in this "B" socket-power unit. Appropriate (should the latter be of the filament type), talares for all purls are piren.

www.americanradiohistory.com 11.0 Radio News for April, 1928 How to Pick An Audio Amplifier

An Elementary and Unbiased Discussion of the Resistance - Capacity, Impedance- Capacity and Transformer -Coupled Types

By Fred H. Canfield

U DIO- FREQUENCYENC1 amplifiers falll properly designed, is capable of providing music. This is contrary to the fact. No into three principal classes, viz.: the saine high quality of reproduction. It amplifier has yet been developed which is transformer -coupled, resistance -ca- should be explained that there are such entirely free from distortion, even though pacity- coupled and impedance -ca- questions as first cost, efficiency, ease of the actual amount bas been reduced to a pacity- coupled, or combinations or modifica- construction, etc., which should be con- very low minimum in some instruments. In tions of these three types. During the past sidered. For an example, compare the re- the case of the resistance -capacity -coupled few years newspaper radio sections and sistance- capacity- coupled amplifier with the amplifier the fact, that the resistor units are other radio periodicals have published much standard transformer-coupled amplifier. In impartial to the frequency of the currents propaganda in favor of and against each most cases the first cost of the former is they amplify, is probably responsible for of the three systems; with the result that the much less, but the efficiency per tube of the "distortionless" claim, but two other general public is greatly confused on all the latter is much greater. Therefore, it possible causes of distortion remain. First, Matters concerning the subject. In this may be seen that in this particular instance the impedance of the coupling condensers article no attempt will be made to give a it is necessary for the owner to decide which varies inversely with the frequency of the definite solution to the riddle, "What is the is the more desirable feature. But these current and as a result the low notes are best type of audio not amplified at full amplifier?"; but the volume; and second, writer will endeavor the tube will intro- to point out the de- duce distortion if it is sirable and undesir- not operated with the able characteristics of Correct bias applied each arrangement. to the grid. Also, This information overloading any stage should aid the reader of this amplifier will in deciding the par- Cause distortion, just ticular combination of as in any amplifiers which will instruments !E P PRI B7 of other types. best satisfy his re- Another false im- quirements. pression which the ad- In the first place, it vocates of resistance

should be explained .... . fric, ár, ;r, r capacity -coupled am- that it is impossible i plifiers have tried to to say that one basic establish is that a audio -amplifier circuit is better than an- Three different types of audio transformers arc transformer -coupled amplifier min ti cause shown in the above illustration. The two large other, as every amplifier has limitations or units are of modern design and are highly distortion. This is true in the strict meaning features which may be considered objection- efficient, while the one in the center is typical of the word, but the authors of the statement of the old -type instruments, which were small able. On the other hand, with any one of and inferior. tried to create the understanding that the the three types described in this article, it distortion in such units is always excessive. is possible to obtain reproduction which is are not the only questions which must be 'l'he fact is that, under ideal conditions, the practically perfect, provided the amplify- taken into account. reproduction would be so natural that any ing units have been correctly designed by further improvement could not be detected an experienced engineer. It is, therefore, DISTORTION NEVER ABSENT by the human ear. necessary for the set builder to sum up all Before continuing further with this dis- Now that a few facts about amplifiers the facts he can learn about each amplifier cussion, the writer wishes to correct one in general have been made clear the differ- and then decide which is the most desirable impression which seems to exist in the mincis ent types of amplifiers may be considered for his purpose. of a large number of radio amateurs. The separately. In Fig. 1 there is shown the At first thought it may be difficult for the statement has been published frequently, schematic wiring diagram of a standard re- beginner to understand exactly where the that resistance -capacity -coupled amplifiers sistance- capacity -coupled amplifier. The cir- problem lies, if each type of amplifier, when do not introduce distortion into speech or cuit shown employs three stages, which is

Tlic amplifier illustrated at the left is a standard, factory. built, a typical, home.máde, impedance.capacity-eanpled amplifier. Both three- stage, resistance- capacity-coupled unit. At the right is shown units are small in size and furnish very satisfactory reproduction.

www.americanradiohistory.com Radio News for April, 1928 1141

the circuit entirely and substitute a "C" battery of the proper voltage at the point C VI V2 C V3 marked X; but, as the voltage of the "C" battery would have to be equal to the volt- xI age applied to the plate of the preceding tube, plus the potential required for biasing Rÿ O Ì RG the grid, this is an impractical arrangement. Therefore, it is usually necessary to select I- D for the coupling condenser a value which a does not cause too much distortion, and z RP RP then to use a grid leak which gives most satisfactory results. The value of the con- denser nay be as high as 0.1 inf. if great volume is not required from the receiver; 1i'II I but when it is desired to operate a loud speaker with good volume it may be neces- sary to reduce the capacity of the condenser MIMI111111111111 to .01 inf. The size of the grid resistors must be determined by experiment and the highest value which gives satisfactory results on loud signals should he selected. In many FI G. 1 O cases it will be found that best reproduction V. B+ 180 V. A- B- A+ C-3V. C- 40 is obtained when a comparatively high re- C+ sistance is used in the first stage, a lower Schematic miring diagram of a typical resistance -capacity -coupled audio -frequency amplifier. RP, resistance in the grid circuit of the second plate resistors; RG, grid resistors; C, coupling condensers; VI and V2, "hi -mu" tubes; 1/3, stage and a much lower resistance in the power tube; LI -CI, output filter. grid circuit of the power tube. 'l'he value of the resistors may vary from 2 megohms the number usually re-piked for loud- 240 tube, with a 250,000 -ohm plate resistor, to 500,000 ohms. speaker volume. the plate potential should be 180 volts. In circuit arrangement the resistance - Under these conditions a grid bias of 3 capacity- coupled amplifier is very- simple. volts is required. ELIMINATING R.F. EFFECTS The plate voltages for the first two ampli- Probably the most important problem in In operating resistance -capacity- coupled lier tidies (V1 and V2) and the detector the design' of a resistance- capacity- coupled amplifiers there are several things which tube are applied through three resistors amplifier is that of the proper values for should be remembered. In the first place, (ltI'). The plate of one tube is coupled the coupling condenser and the grid re- amplifiers of this type amplify radio -fre- to rho grid of the tube in the next stage sistor. In this connection there are three quency currents ,just as well its audio-fre- by means of a condenser (C), which pre- things which must he renumbered: first, quency currents and, to prevent the tubes vents the plate potential front being applied distortion is reduced as the rapacity of the from being overloaded with It.F. potentials, to the grid. 'l'he resistors lt(i in the grid coupling condenser is increased: second, it is essential that a radio- frequency choke circuit of each tube complete the circuit the amplification is increased as the resist- coil shall be connected in the plate circuit between the grid and filament and make it ance of the grid resistor is increased; and Of the detector tube. Also, a small by -pass possible for the grid charges to Irak to the third, as the values of the coupling con- condenser (approximately .002 inf.) should filament. denser and grid resistor are increased, a be connected between the detector plate and Although the circuit of the resistance- time lap tends to destroy the utility of the the filament. Secondly, if a power tube of capacity-coupled amplifier is not in the least amplilicr. 'l'he time lag is caused by the the 210 or the 171 type is used in the last complicated, the selection of the proper sizes fact that the grid resistor is unable to dis- stage, an output filter or output trans- of resistors and coupling condensers, and charge the coupling condenser rapidly former of some type should be connected the lise of the proper kind of tubes, is enough when loud signals are being received in the plate circuit to protect the windings highly important. If the various pieces of and, as ut result, the grid becomes blocked. of the loud speaker from the large value apparatusu-atus used in the amplifier are not From the above it may be seen that two of plate current used by the power tube. suited to the respective purposes for which conflicting conditions exist which prevent Thirdly, an efficient source of "B" supply they are used, the amplification will be very the amplifier front delivering perfectly dis- must be employed and, if a "B" power unit 1ow or the reproduction will be very un- tortionless reproduction. Of course, the with as high output resistance is used, spe- satisfactory. ideal solution would be to eliminate the cial precautions must he taken to prevent coupling condenser and grid resistor from "motorboating." These arc discussed later. RESISTANCE VALUES In the first place it should he explained that the amplification obtainable from this type Of amplifier depends entirely upon the am plilication factor ('mut ) of the tubes employed. For this reason the 201A -type tube with an antpli0cation factor of 7 is not entirely satisfactory, and a tube of the 2411 type. with an amplification factor of :30, should be selected. Secondly, the plate resistors should have as high it resistance as possible and in no crase should the valve of these resisla1s be less that the plaie resistance of the tube. In the case of the 210 tube the plate resistance is 150,000 ohms and, in order to obtain satisfactory ampli- fication, the plate resistor must have a re- sistance of at least 250.000 ohms. A third important factor is the selection of the proper plate voltage. Because the resist- ance of the plate resistor is always greater than the plate resistance of the tube, more than 50% Of the plate voltage is wasted in the plate resistor. Therefore, it is im- perative that a high voltage be applied to the resistor, in order that the plate shall receive sufficient potential for the efficient The circuit arrangement of a typical impedance -capacity-coupled audio -frequency amplifier. LP, plate impedance units; RG, grid resistors; C. coupling condensers; VI, 1'2 and V3, vacuum opt-ration of the tube In the case of the tubes; LI -Cl, output filter.

www.americanradiohistory.com 1142 Radio News for April, 1928

Lastly, best results will usually be obtained when a 240 -type tube is used in the detector circuit with a plate potential of 180 volts TI Vi T2 V2 T3 and a grid bias of 4% volts. To conclude the discussion of resistance - capacity- coupled amplifiers it may be said that they are capable of providing excel- I- 410 ii to lent reproduction when properly designed, D and the total cost is considerably less than a t- that of other types of amplifiers. However, Z D they are not foolproof in operation, as there 1 are ninny factors which may cause severe i distortion. Usually they require more stages than sloes a transformer-coupled amplifier, to produce a given amount of volume. In operation these amplifiers are most satisfac- . tory where large volumes are not required. FIG.4 Also, the tubes in the resistance- capacity- coupled amplifiers require a higher plate C- A- B- A+ B+ C- B+ potential for their operation. AMP. C+ AMP. POWER POWER CHOKE-COIL COUPLING In Fig. 2 will be found the wiring dia- The wiring of a standard two- stage, transformer- coupled amplifier is shown in this schematic wiring diagram. 7.1 and 72, audio -frequency transformers; 73, output transformer; V1, first amplifier gram of a standard impedance- capacity- tube; V2, second amplifier (power) tube. coupled amplifier. From the circuit it may be seen that it is very similar to the re- sistance- capacity coupled type, the only dif- amplify is three or four times as great as " "MOTORBOATINO" ference being that audio-frequency choke the output resistance of the vacuum tube, coils (Lp) are connected in the plate cir- the distortion from this cause is not serious. ":Motorboating,' probably more than any other single factor, has prevented amplifiers cuits of the stages in place of the resistors Choke coils which have an inductance of used in the resistance -capacity am- of the resistance- capacity- and impedance - -coupled 100 henries or more are satisfactory when plifier. In operation is very capacity- coupled types from achieving this amplifier using the 201A -type tubes. the im- similar to the resistance-coupled type, but With greater popularity than they have done. It it is more economical as to plate voltage; pedance- capacity- coupled amplifier the dif- may be described as a form of interference, as the large voltage drop across the plate ficulty in obtaining a satisfactory value for heard in the reproduction, which sounds resistors is obviated by the substitution of the coupling condensers and the grid re- like the exhaust of a motorboat's engine. choke coils. It is also easier to obtain a sistor is identical with the problem in the It is most annoying and sometimes ruins degree of amplification which closely ap- resistance -capacity -coupled amplifier. reception. It is seldom heard if the am- proaches the amplification factor of the From the above it may be seen that the plifier is supplied with a plate potential tube than with resistance- capacity coupling. impedance- capacity -coupled amplifier is al- obtained from batteries, but is very fre- This is because, in a resistance amplifier, most identical with the resistance- capacity- quently the cause of unsatisfactory results the value of the plate resistors must be coupled amplifier in operation, circuit de- when an inefficient socket -power unit is used. several times the output impedance of the sign. and construction, and produces very The elimination of the "motorboating" effect tube before the amplification of the stage similar results. It will give equal results puzzled radio experimenters for a long time, approximates that of the tube. with lower values of plate voltage, but the but several methods have been found for In the impedance -coupled amplifier the parts used in its construction are slightly overcoming the disturbance. audio -frequency choke coils vary in impe- more expensive. When operating the im- Motorboating can frequently be eliminated dance with the frequency of the current pedance- capacity -coupled amplifier in con- by correcting the design of either the am- which they amplify, and as a result the nection with a plate -power-supply unit one plifier or the socket -power unit; but the amplifier gives slightly better results on is apt to experience a "motorboating" effect most satisfactory method is to attack the high notes than on low frequencies. How- unless provision has been made to guard trouble at the source, the socket -power unit. ever, if the impedance of the audio choke against it in the design of the amplifier It has been found that socket -power units coil at the lowest frequency which it is to or the power unit. which have a low output resistance and an adequate filter, and which provide a con- stant voltage, do not cause "motorboating." Also, it has been found that by the use of an 874 -type (voltage-regulator) tube in the output circuit of a socket -power unit, the current may be made constant and the out- put resistance may be reduced at the sanie time. The problem of improving the filter need not be discussed, as this is merely a matter of selecting efficient apparatus. If it is desired to make changes in the ampli- fier, a 3 -henry choke coil, connected in the plate-supply lead of each stage, often pro- duces the desired effect. If the choke coils do not entirely eliminate the trouble, the use of an impedance leak in place of the grid resistor in the last stage often improves results. Sometimes it will be found that, by alternating between stages of resistance - capacity- and impedance -capacity- coupled amplification, one can obtain even better performance. A typical combination of this kind is shown in Fig. 5. While on the subject of impedance -ca- pacity- coupled audio amplifiers, it should be pointed out that there is a variation of the circuit which makes it possible to obtain an amplification greater than the amplifica- tion factor of the tube, and still retain the The amplifier shown in the above schematic diagram employs a combination of resistance-capacity advantages of this type of amplifier. The and impedance- capacity coupling which proves very satisfactory. "Motorboating" is usually absent in this circuit. (Continued on page 1162)

www.americanradiohistory.com Radio News for April, 1928 ]143 Transmitting on a Wavelength of Three- Quarters of a Meter Remarkable Work of German Fxperimenters With Radiophone on Ultra -High Frequencies Develops Interesting Circuits By H. E. Hollinann*

OW wavelengths.' and "Thigh fn.- Today there are many high -power com- bered that the results described were ob- quencics" are radio terms which mercial stations operating on wavelengths tained with foreign equipment and, there- may be considered as entirely which were considered entirely impractical fore, entirely different results may be ob- L relative, as they have no particular less than six years ago. It has been found tained from American tubes and apparatus. significance of their own. Several years ago that the very short waves possess many un- Two German radio engineers, Bark- all channels below 600 meters were classed usual characteristics which make them ideal 'as "short waves"; and, when the American for certain types of communication,nicatiou, par - radio law of 1912 was passed, the legislator:. ticularly over long distances. In addition P P, thought that the amateur transmitter could to the stations which are actually operat- be eliminated by assigning stations of this ing on short waves, there are hundreds of C class to wavelengths below 200 meters, as experimenters endeavoring to obtain data on this field was considered valueless. When the ultra-short wavelengths which have not broadcast stations started operating on yet shown their commercial value. waves the amateur band, the amateur While engineers are busy trying to find near Io was forced to use still shorter wavelengths; some commercial use for the wavelengths Ip and at that time it was discovered that sat- below 13 meters or so, scientists are still o isfactory results could he obtained on less seeking shorter wavelengths to conquer. In than 100 meters. Later amateurs found this field the latest development is a new that waves as low as ho meters provide transmitter which operates on a wavelength valuable channels for communication. of 75 centimeters (three -quarters of a meter, or 891,4; inches). Of course, no prac- Eg tieal use has vet been found for such a Ep transmitter, but the inventors of the sys- II tem are very much pleased with the fact Ef that they have been able to produce oscil- lations at such high frequencies, and are FIG. 1- equally elated over the development of a receiver which will detect the oscillations. Not only have they been able to transmit The 75 -cm. resonant circuit comprises only the and detect continuous -wave signals on a parallel wires of length (t) varied by the slid - 13, tine internal capacity. wavelength of 75 centimeters, but they have ing bridge and tube's been able to send and receive I.C.W. (in- terrupted continuous wave) and even tele- hausen and Kurz, are responsible for the phone signals on these high frequencies. first research work attempted in this direc- These signals have been received over dis- tion. The discovery which pointed to the tances of approximately a quarter of a mile. possibility of operating radio apparatus on wavelengths of less than one meter came PRINCIPLES UTILIZED as a result of a study of the characteristic curves of vacuum tubes. It was found that In this article no attempt will be made to in these graphs certain irregularities ap- give constructional details of n receiver or pear, which are similar to the resonance transmitter for operation on 75 centimeters, curves obtained in high- frequency phe- but the experiments with this apparatus nomena. In the experiments which fol- which have been conducted in Germany will lowed this discovery it was proved that be described for the benefit of the qualified high -frequency oscillations can be produced experimenter who may wish to do some by applying a high positive 'potential to the original research work with ultra -short grid of a vacuum tube and a negative po- wavelengths. However, it must be rentem- tential to the plate. Measurements were made which showed that the oscillations which were produced in this way had a fre- V quency ltreater than one hundred million cycles per second, corresponding to a wave- T length less than three meters. Barkhausen and Kurz explain the results described above as follows: the electrons emitted from the incandescent filament are The telescoping hori- so strongly attracted by the positive grid zontal rods A form that they move at high speed across the the only atrial of the 75 - centimeter space between the filament and the grid, and radiophone transmit- into the space between the grid and the ter at the left; they are slid up and plate. As the electrons approach the plate, down the vertical they are strongly repelled by the negative mast to decrease or increase the length potential and, as a result, arc driven back of flic way - .._:._ ...»....>....,.,.._.. parallel wires toward the grid. In this a pendulum included in the os- movement is around the cillatory circuit of like established A the tube VI, and grid; or in other words, electrical oscillar 1(r}i connecting the tatter with its batteries. tions are produced. The frequency of the oscillations has been found to be governed by the characteristics of the vacuum tube ' l'hysical Institute of Technology, Darmstadt, GCMGoy. and the value of the plate and grid poten-

www.americanradiohistory.com 1144 Radio News for April, 1928

that by connecting a closed oscillatory cir- comparing the two curves of the graph, it cuit to the tube it is possible to obtain a may F-Ip IN MILLIAMPERES be seen that the maximum intensity of considerable increase of energy. is r-R.F. MILLIAMPERES oscillations approximately at the point of The circuit which he used for this pur- maximum plate current. Therefore, by ad- 30 150 pose is shown in Fig. 1. Two parallel wires justing the bridge until maximum plate cur- (P and Pl) are connected to the grid and rent is obtained, it is possible to determine 20 100 plate terminals of the tube, and these wires the frequency of the oscillations by meas- are connected by a sliding bridge, B. The uring the length of wire in the bridge; and, 10 50 grid -plate capacity of the vacuum tube, plus at the same time, be assure of maximum the inductance of the two parallel wires, intensity of oscillations. The curves shown 30 40 50 60 70 80 90 100 composes the closed oscillatory circuit, were obtained with a Schott transmitting LENGTH (1) which may be adjusted to the desired fre- tube (type N) under a plate potential of IN CENTIMETERS quency by the sliding bridge. The grid and 240 volts. -FIG. 2- plate potentials are brought to the tube through the parallel wires and the by -pass USE FOR TRANSMITTING condenser (C) is used to prevent a short - order to Maximum plate current in the 75 -cm. trans- In convert the oscillator de- mitter practically coincides with maximum os- circuit of these power -supply wires. Be- scribed above into a short -wave transmitter, cillatory current; thus making tuning possible. cause of its relatively large capacity, the it is necessary only to connect a bi -polar presence of the condenser in the bridge has antenna to the bridge in the proper man- or no effect upon the high- Bills. The oscillations are accelerated by little frequency ner (see Fig. A). Such a transmitter will circuit. an increase in the potential producing them, send out a considerable amount of energy, and vice versa. and, with proper modulation, will serve for radio telephony. 'rte bi -polar antenna con- SPECIAL TUNING CIRCUIT sists of two straight wires (each half as long as the wave produced), which are fast- The research of Barkhausen and Kurz ened directly to time bridge in a horizontal has been confirmed by Scheibe, another position, in the manner shown in the pic- well -known German scientist, who has in tures accompanying this article. In Fig. 3 addition developed an exact formula by the complete schematic wiring diagram of a which the frequency of the oscillations may transmitter of this type is given. The bi- be determined in every case. With the polar antenna is shown At A and is con- method described above, Scheibe found the nected directly to the bridge C. The two oscillations very feeble, and only with the inductors in time filament circuit are choke most sensitive indicator was he able to de- coils which prevent undesired self- oscilla- tect their existence. However, he found tions.

DIFFICULTY OF ADJUSTMENT D Development of apparatus for receiving signals from transmitters operating on a A A' A graph of the sensitivity of the 75 -cm. an- tenna as it is revolved trough 360 degrees. wavelength of less timan one meter pre- It is very directional. sented another problem which scientists did not find easy to solve. With signals hav- ing a frequency of approximately 400,000; A TWO-WAY CURRENT 000 cycles per second, it may be seen that The operation of such a circuit as shown time usual method used for receiving con- in Fig. 1 may be explained as follows: with tinuous -wave signals (i.e., the audio beat - a negative potential applied to the plate, note system) would be entirely impractical; under ordinary circumstances, it would seem as it is almost impossible to adjust the fre- that there should be no current between the quency of the receiver so exactly that the plate and the filament. On the contrary, in oscillations received from the transmitter, a poor vacuum tube it is possible to detect when "beating" with the locally -generated an "ionic" current flowing in the opposite oscillations, would produce a steady audio direction from that of the normal stream of note. Therefore, another system was found electrons. If oscillations are now produced necessary and I. C. W. and phone were in the tube, in the manner previously de- tried; both of these proved satisfactory. scribed, a positive stream of "ions" will be found to exist; and this stream' will reach In their original experiments Bark-hausen its maximum when resonance is produced and Kurz endeavored to modulate the out- between the outer oscillatory circuit and the put of the set with a buzzer connected oscillations inside the tube. The ion repre- in the plate circuit of the tube. However, sents a particle of gas which has lost an this proved entirely unsatisfactory because, electron (unit negative charge) and there- when the plate circuit was opened, the grid fore has a unit positive charge; it tends to move toward a negative potential, there- fore. J With a milliammeter (Ip) connected in the plate circuit, it is possible, by observ- ing time current registered on the scale, to determine with certainty the best position for the sliding bridge. It is possible also to measure the frequency of the oscilla- tions. Fig. 2 shows that the plate current of the tube (the solid line of the graph) varies with the length of the wire in the bridge circuit. The dotted line of the graph indicates how the R.F. current of the closed R oscillatory circuit varies with the length of wire in the bridge. This measurement was obtained by con- necting a thermo -coupled milliammeter in A 75 -rm. receiver of the simplest type, with series with the condenser (C) and in this crystal detector D, and sliding bridge A -:11. way L are R.F. chokes; the phone leads are inside the high- frequency current in the bridge was The circuit of the 75 -cm. vacum -tube receiver the vertical rod. circuit directly measured. By pictured in Fig. C.

www.americanradiohistory.com Radio News for April, 1928 1145

phenomenon; if the waves from the trans- mitter or the receiver are thrown back or reflected by a metal plate, they will then interfere with the direct transmission and, in this way, there are produced "standing The accompanying circuit waves" which can be recognized by the ris- diagram contains the de- ing or falling of a galvanometer needle. tails of o transmitter op- erating on 400,000 kilo- 'l'he apparatus is so sensitive that waves cycles, or A -meter (75 reflected at a distance of several meters centimeters), and capable can be observed. of send in g plane or I.C.W. (buzzer) signals. The intensity of reception is at maximum It will he seen that there when the transmitting and the receiving is a NEGATIVE voltage on the plate and a POSITIVE antennas are parallel. If one of them is on the grid; and the turned through 90 degrees, the reception modulation system is un- usual. These peculiarities disappears completely, and then by further arc necessitated by the turning is brought again to maximum. Plot- unusual conditions en- countered at such cnor- ting the galvanometer changes with polar rmu sly high frequencies. coordinates produces a graph for a bi -polar antenna similar to that shown in Fig. 4.

LATEST DESIGN For reception over greater distances, we have to design an efficient vacuum -tube re- ceiver. After various experiments the dr- received the entire emission current and, the two parallel wires are carried up the cuit shown in Fig. 5 was chosen, and this as a result, quickly overheated. In Fig. 3 sides of the rod. The bi -polar antenna (A has given very good results. V is a vacuum the buzzer (B) is shown connected directly and Al) and the sliding bridge are also tube, with a grid condenser (C) and a in the grid circuit and this has been found mounted in much the same manner. The grid leak (R) of one megohm. The oscil- to he very efficient. wires to the headphones go up the inside latory circuit is formed ,just as it is in the Barkhausen and Kurz also attempted to of the rod and the escape of R.F. currents transmitting circuit, with two parallel wires modulate their transmitter for telephone, is prevented by small choke coils (L.) on which slides the bridge extending to but the results have been more or less un- If, in place of the headphones, an ex- the antenna. Now, as only the plate po- satisfactory. A modulation transformer tremely sensitive measuring instrument is tential is carried over the parallel -wire sys- was used to replace the buzzer in the plate- connected to the detector circuit of the tem, the condenser portion of the bridge is supply wire, and a microphone was con- receiver, the transmission of short waves superfluous. The tuning in of the signal nected in series with the primary winding. through space can be observed and investi- from the transmitter must be accomplished This method, however, modulates only a gated. Here we must refer to an observed by sliding the bridge and by lengthening small percentage of the output. or shortening the antenna. The tuning of the oscillatory circuit with these methods is TELEPHONE WORK extremely difficult and the highest sensi- 'l'he only experiment which has given tivity is finally obtained by variation of the satisfactory results employed a circuit such plate potential. as is shown in Fig. 3, in which an extra Fig. C shows the receiver as it appears tube is used as a modulator. In this cir- completed. As in the detector circuit pre- cuit the fluctuating current of the micro- viously described, the high -frequency section phone (M) is carried through the micro- must be withdrawn as far as possible from phone transformer ('l') to the grid of the the disturbing influence of the ground, and modulating tube (V) and this changes the supported on the vertical insulating tube. internal resistance of the tube so that low - The apparatus shown in The circuit constants with ultra -short waves the illustration at the are very of frequency potential variations exist in the right is designed to re- small; so that the entire length choke coil (L). As a result, the grid po- ceive signals down to a the system of parallel wires is only about the wavelength as short as 50 millimeters (two inches). The connec- tential of transmitting tube (V1) is half a meter. The capac- increased and diminished in accordance ity of the tube is so high, tions to the battery lead are brought down with nid relation to this ire - through the rear of the tube. To increase the voice frequency. quency, that only about Figure A gives a complete view of the TWO INCITES of the paral- the amplification of the receiver, a Loewe radio- telephone lel wires extending to the triple tube (three sets of elements in one transmitter which has been hase of the tube is re- designed to operate on a wavelength of 75 quired in the tuned oscil- glass bulb, as described in Ranno NEWS for centimeters. The two parallel latory circuit. The aerial July, 1926) is connected in an audio am- wires (P lies across these at right and l'1 in the diagram) are supported by angles, and moving it plifier circuit. With this apparatus, it is the wooden pole and the oscillator tunes the receiver -a very possible to demonstrate to a large number tube delicate operation. Three V1 is mounted on the top. The sliding stages of audio cmplifica- of listeners the phenomena of fixed waves, bridge and the bipolar antenna, (A -C) tion are combined in the interference, reflection, etc., by means of single tube on the battery which are adjusted to tune the closed oscil- container. a loud speaker. The experimenters have latory circuit to resonance with the trans- covered a distance of about 300 meters; but mitted frequency, are provided with a tele- the intensity of the sound was still so great scoping brass rod. B is the buzzer which that the limit has been by no means reached. is used to modulate the system for teleg- raphy, and the telephone modulation equip - ment is located to the right. The designat- ing letters of all parts correspond with those in the diagram (Fig. 3.) The 120 storage cells located under the table are used for providing the grid po- tential to the oscillator tube.

THE RECEIVER The apparatus used for receiving signals on wavelengths of 75 centimeters is shown in Fig. B. The construction of the receiver is very similar to the transmitter, although the circuit is somewhat different. The long wooden rod supports a crystal detector in an insulated tube (D) at the top, and

www.americanradiohistory.com I 1 1 . Radio News for April, 1928 Letters from Home Radio Set Constructors

EARLY WORK IN RADIO and two power tubes, with 200 volts "B "; this want, and that is another aerial in the other direc- hook -up will bring a symphony concert to your home tion; the one I have is east and west, and all sets Editor, RADIO NEws: in proper style. should have aerials north, south, east and west. I I read the Somersalo frequency -filter article with I am an old radio bug -since 1919 -and distance have proved this by trying previous sets for months interest, because the first receiver I ever built had does not mean anything to me; but on quality I'm at a time, first on a street east and west, and then three stages of manned R.F. amplification. After a crank. I always enjoy reading your magazine, on a house whose street lay north and south. An months of experiment, I was able to secure razor - and I can boast of having all your copies. Should aerial in one direction only is directional, like a edged selectivity with this receiver. It was used anyone wish any more information, I will gladly loop or a superhet. You don't notice it, because to give concerts in small towns in Louisiana and write to anyone. you can't move it around; but put another aerial Arkansas, and was the first radio set seen and heard J. LARDEMER, in the crosswise direction, and you will get sta- by thousands of people. 355 Douglas Street, San Francisco, Calif. tions you never had before op the sante set. The signal was first selected by a single -tube (Our caution should be repeated; readers should I am going to write you again in the near future regenerator, having a lamp -cord aerial about 20 not write for elementary radio information, or for -don't forget I ant 500 miles north of you, up in feet long. This regenerator was in a separate cabi- instructions on points which should be apparent to Canada. I have had the set working one week, and net and placed a few feet away from the other anyone Tao has the mechanical or electrical skill here are the stations I have logged. (List of 51 receiver and its loop. The regenerator had the necessary to build such an installation. The equip- stations in the United States and Canada, ranging regeneration control for all stations, hence opera- ment pictured here is an excellent combination for to St. Petersburg, Fla., and Fort 'Forth, Tex.) tion was easy. The signal radiated by the regener- those who have a suitable +wok in which to install and a bunch more that I haven't had time to log. ator was picked up by the loop. It was found ad- it. The speakers might well be tested in series and I will send you a full list later on. I might also vantageous to place a R.F. choke and "C" battery in parallel. In previous issues of this magazine state that I think those who buy RADIO NEWS buy between the loop and the potentiometer lever, be- full directions have been given for a connection all there is in radio literature. I have tried them cause the latter then had the same setting for all which permits, with the aid of a suitable switch, all. Again allow me to thank you. Yours in at, stations, and the selectivity was improved. The all possible combinations of one or both. - preciation, JOSEPH ADAMSON, combination of receivers was operated as a two- EDtroR.) 14 Balsam -Avenue, North,, Hamilton, Ontario. dial tuned set, and it was not necessary to readjust either the regeneration control or potentiometer MISSIONARY WORK lever. It was necessary that the coupling between A SATISFIED SET BUILDER Editor, RADIO NEws: the regenerator and the loop should be very loose. Editor, RADIO NEWS: An outdoor was never needed. You are a friend me for publishing the aerial to have noted, C. J. ROGERS, Peridyne Five. I have built three or four sets tip I carefully, practically every circuit that you have published in your magazine Mc: ilen, Texas. to now, and when I read that article, I thought for the past five years; "This fellow is making a broad statement, but it but I ant still using a five -tube reads good to me." I am using a four -tube re- RADIO IN THE FIREPLACE generative set, and four other fellows at the sante ..1111111111111 ...... 1::1..k..1..1..1 l.... l.l..11.l..l..l..,...... 1....11..,..1 .....l..l....,.,,v1,1...1o....l 1...... ,.s..... plant had the same kind, and they thought they Editor, RADIO NEWS: had the last word in radio; all were bugs of five for this page should be as In your editorial, "\\lint's \\'hart in Radio, you or six years' standing. LETTERSshort as possible, for so many are re- mentioned that two speakers will give the best Well, my set has two .0005 geared condensers, ceived that all cannot be printed. Unless music. \\-ell, "you said it;" and if anyone wants so I bought one more and made all the coils, and a set is made from a published descrip- to go to the trouble to do what I did, he will be cans of copper about .02-inch thick; and for about tion, a schematic sketch should be sent; photos can be used only to illustrate a well repaid. I have been using for over a year $10.00 completed the set out of the tour -tuber I novelty, and then only if large and very now the combination shown in the diagram; and was using, with only two alterations front the pub- clear. Inquiries for information not given ninny of my friends who have heard this outfit lished circuit (three condensers instead of a gang here should be sent to the constructor have asked me to write to you and let other fans and a resistor of 10,000 to 700.000 ohms). I used direct; but he should NOT be asked to know what can be done. 201A tubes throughout, and 22V volts on the first furnish data already published, here or First of all, when you enter my listing -room, you audio tube, 90 on the second, with a 4% -volt "C" elsewhere. cannot detect a wire, speaker or set. The receiver, battery. This department is for free discussion '11" potter unit and switches are in my bookcase, I want to tell you, honestly, the owner of an to the extent that space permits; but and the speakers arc in the fireplace, hidden be- 8 -tube superhet and a battcryless 6 -tube set with RADIO NEWS accepts no responsibility hind a Chinese screen. All wires, including the 180 volts on the last stage, admitted I had him for the opinions of readers as to the rela- aerial lead -in and ground, are in the walls. The beaten with my five -tube Peridyne. I brought one tive merits of apparatus and circuits. ".\" battery and trickle charger are in the base- of the fellows from the plant down to the house; ,..1sv1o..,..1.11.vw1 1 ment. When the switch C is thrown up, it con- he had had a four -tuber for a couple of years, and lllll .l..l ..1,111...11...... 1..1..1....11..1..1....l...l . l..,...... l..,....l..... 1..1..1...11.1.1 l....l nects the battery with the set, ready to operate; thought it was "it." Well, he stayed four and a when the switch is down, the charger is connected half hours, and went honte; and the next night he neutrodyne which I constructed from Fada parts and switch E starts it charging. The double socket tore his set down and started making the Peridyne over three years ago, and I have found no other D gives a place to plug in a lamp. shields. The other three fellows who have the circuit any more satisfactory for my use here To get really good reproduction, the fireplace same old set are coming down this week to see it, the country, where I am located, sixteen miles should be hung with heavy velvet; but in order to and, of course, I know what will happen. The west of Richmond on the James River. get a good soundbox, I first had it lined with fellow that heard mitre told one of them, confi- Speaking of DX reception, I can nearly always linoleum. The horn is a Rola and the cone a West- dentially, that mine was 100 per cent. better than get KFI on the loud speaker, and with good vol- ern Electric. Just at this time there is organ music theirs. ntnte, at any time at night during their broadcast on the radio, and I tell you it is a pleasure to Anyhow, I am perfectly satisfied with this out- ing hours, except when \ \'RC at Washington is on listen to it. I am using Thordarson autoformers fit, and then some. There is only one thing T the air. When Lindbergh was in Mexico City, I was prompted to tune in for the G.E. station there (CYJ) and experienced no difficulty in hearing the station clearly before 9 o'clock in the evening. My success with my receiver is clue principally to the fact that I am using regeneration in addi- tion to the already excellent amplification of the neutrodyne circuit, which results in a real DX- getting set. The method of doing this success- fully was first brought to my Il IIG ( ar attention by a most -- interesting article by Mr. A. L. Graves, "The Re- generative Neutrodyne," published in RADIO NEws in April, 1925. Instead of getting regeneration Imo. B ° from a variometer in the detector circuit, I ant h i _ using a winding which was inserted in the tube of s! D. °- the second R.P. transformer; regeneration being f a ó controlled by _._ variable condenser in series seitlt DIS this special winding. I can get all the regenera- D INN .: i ISOIN IC .. :'. "PPalnom._ - tion desired with fine control throughout all the .:- wavelengths from 200 to 575 meters. I am using

11 five C \' -201A R.C.A. tubes, and three IM _MI=l!! o of them bbd _ e,. la01 0 .111 II) have given over 3,200 hours' service and are still _ HIM doing good work! W. D. Moss, M.E., `aülül "Huguenot," R.F.D., Moseley, Va. Hi A- OUTPUT TRANSFORMER 10V. B- "B" POWER UNIT -4 VARIABLE TAPS LINE ECCENTRIC CONE WORKS WELL C- DOUBLE SWITCH TO SET AND CHARGER Editor, RADIO NEWS: _. D- HOUSE- CURRENT SOCKETS ' The second prize wrinkle in your January issue E- BATTERY-CHARGER SWITCH . interested me, as the possessor of one of the origi- nal Crosley Musicones. I tried out the eccentric F- STORAGE BATTERY cone idea and really believe Mr. Crosby should i have been awarded first prize. G- SPEAKER LEADS je. 1 ' Int making the new cone I used Fonotex paper H- FLOOR and found that in the small cone for the apex - I I - TRICKLE CHARGER .'- - had to cut out seven- eighths, instead of five - eighths, to get a snug fit. I made a light wooden frame mounting for the Mr. Lardemer's reception room makes use of a tastefully- screeneá fire place. The arrangement Crosley unit and, as the weight of the new cone is shown above, and its convenience is apparent at F. glance. hanging on the rather small actuating pin of the

www.americanradiohistory.com Radio News for April, 1928 1147

reason why the contrivance 1 had built should be It works very well with the simple "B" power worth a cent as a loud speaker, or even speak at unit described in the April, 1927, issue of SCIENCE all. AND INVENTION. This unit works very well with a However I hitched it up and turned on the set; 201A tube, but I am using a 21611. All fans who result, the finest -toned speaker I have ever lis- want a good power unit that works as well as bat- tened to, and I have heard the Radiola, Western teries should build it. Anyone wanting information Electric, Peerless and all the rest of them. The on either can get it from me by sending a letter tone was unbelievably pure, true and natural, low or card. IIERCERT L. TRAYLOR, JR. notes just right in volume and absolutely no sounds (We will do Mr. Traylor a favor by leaving out that should not be there. I have more respect his address, because we know what will happen as for the little Crosbey unit than before. a result of his generous offer, if tec do not. To Should have said that I built the 20 -inch cone make his DX record clear, however, toe may say which, I believe, is plenty large enough for home that he is a resident of Virginia. The 'met-flex use where quality alone is desired. Would like Four is an early design using the sane principle to try it again, but am afraid I would never again which is exemplified, with improved components, in have such luck. the Pcridyne Fire. Some constructors, however, C. E. CURRIER, cling to the earlier and simpler model, with which 1476 Belmont St., N. W., Washington, D. C. Mr. Hurley's atrial, showing how great length some remarkable results have been obtained. - is obtained in small space. His letter is on EDITOR.) pane 1191. AN OLD FAVORITE Editor, RADIO News: AN "SOS" COMES IN unit caused it to assume a position with the long Recently I constructed the Interflex Four, de- Editor, RADIO NEWS: diameter toward the bottom, I had to remount the scribed in the September, 1925, issue of RADIO HELP! Since the publication of my letter in unit and cone on a longer upright shaft. NEWS, and I find that it is the best four -tube set the January issue of RADIO News letter, The weight of the cone caused the short, or top that I have ever seen or heard. The volume is -which by the way, I did not intend you to part, to lean over against the top edge of the cover good, it has remarkable tone quality, and it's fine publish-re- ferring to my success with the RADIO NEWS Short - of the unit, and bent the actuating pin upward into for DX. The furthest station I have received is Wave Receiver, I have been receiving a considerable curve. Believing from what I had KFON at Long Beach. Calif., on the loud speaker. communica- tions in flocks requesting -cad that the pin must always be perfectly straight, I advise anyone who wants a good set to build the all sorts of information and perpendicular to the unit, I could see no Interfiex Four. (Continued on page 1191)

List of Broadcast Stations in the United States (Confirmed from page 1121)

Radio Radio Radio o Radio Call BROADCAST STA. Call BROADCAST STA. Call BROADCAST STA. Call BROADCAST STA « 3q Letter Location Letter Location 1.3 Letter Location f 63 Letters Location

W RM Urbana, 273 WJBU Lcwlsburg, l'a...... 211 100 WLS tChicaco. III 55345 51100 WOAI Stn Antonio. Tes..... 500 5000 III 500 WIBW New Orleans, La 235 30 WLSI See WDWF WOANI Lawrenceburg. Tenn .. 2.10 500 W R M U New York. N. Y. (port) 201 100 WJBY (ladstlen. Ala 231 50 WLTH Brooklyn, N. Y. 25fí 2.Q WOAX Trenton. N. J 240 50 O. Yes, 100326atta500 WJBZ Chicago lleights, Ill 208 100 WLTS Chicaaggo, Ill 484 101) WOBR Shelby, Ohio (portable) 204 W RN Y tNcw- York. Ne WJJD Mooseheart. Ill ^a(i5 1000 WLW tCineinnatl, Ohio 428 50110 WORT Union City, Tenn 205 1:5 (Also meters. WJ KS Gary. Ind 232 500 (Also 52.02 meters. 250 watts) WOBU Charleston, W. Va 268 50 W RP 1 Terree H: ute. d..1 208 100 WJPW Ashtabula, Ohio 2(1.4 30 WLWL }Kearney, N. J. 370 2000 WOC Davenport. Iowa 375 5000 W R R Dallas, Tex 961 5011 WJR -WCX ¡Pontiac, Mich 441 5000 WMAC Cstenovla, N. Y 225 51)0 WOCL Jamestown. N. Y 224 W RRS Racine, Wis. 248 50 (Also 32 meters, 75 watts) WMAF So. Dartmouth. Mass 428 51111 WODA Paterson. N. J 294 1000 WRST Ray Shore. N. Y...... 211 250 WJZ }New York, N. Y.... 45430,000 WMAK }Martinsville. N. Y 545 750 WOI Ames, Iowa 2500 WRUF, Gainesville. Fla...... 297 10 (3XL. 59.96 meters. 30 k.w.) WMAL Washington, D. C 242 50(1 WOK tChlcago, Ill 252 5000 WRVA Richmond, Va. 254 1000 W KAQ San Juan, Porto Rico 322 500 W MAN Columbus, Ohio 234 .0 W 0K Beacon. N. Y 216 500 WSA I ¡Cincinnati, Ohio 361 5000 WKAR East Lansing. Mich... 278 '500 WMAQ }Chicago, Ill 447.2500 WOKT Rochester, N. Y 210 500 WSAJ Grove City', Pa 224 250 W KAV Laconia, N. H. 221 59 W MAY St. Louis. Mo 1110 WOMT Manitowoc. Wis 222 100 WSAN Allentown, Pa 222 500 100 W KBD Joliet. Ill.. . .. 216 150 W MA Macon, Ga 270 WOO Philadelphia, Pa...... 349 500 WSAR Fall hiver. Mass 213 250 WKBC Birmingham, Ala 219 10 WMBA Newport, R. I. (port.) 204 100 WOOD }Grand Rapids. Mich. 261 500 WSAX Chicago. Il!. (port) 204 100 W KBE \Yehster, Macs 229 100 WMRB }Chicago. Ill 252 5001 WOO Kansas City, Mo 341 2F0 WSAZ Huntington, W. Va 250 100 WKBF Indianapolis. Ind..... 252 250 WMBC Detroit, Mich 244 1(1(1 WOR tReamey. N. J. 422 5000 WSB Atlanta, Ci 476 1000 W KBG Chicago. Ill. (portable) 201 1(10 W MBD Peoria Heights, Ill_ 205 250 (.Also 65.4 meters, 50 watts) WSBC Chlrafn. Ill 232 500 W KB La Crosse. Witt 220 500 W MBE St. Paul. Mica 208 10 WORD W S B F St. Louis. Mo...... 441 250 W rßatnvin, IIL...... 25? 5000 WSBT South tV KB I ('hleago. III 216 50 M BF Miami Beach. Fla.... 384 500 WOS JettenlOn City, Mo.... 422 500 Pend, Ind 400 500 W KBL Monroe, allah 205 15 W MBG Richmond, Va 220 50 WOW WSDA see WARS. Omah.3, Nebr 503 1000 WSEA Virginia W KBN Youngstown, Ohio.... 214 50 W M5H Joplin, Mo 204 100 Wayne, pod 229 .2500 Brach Va 261 250 Jersey N. J 219 500 W MB! }Addison, 63 wowo Fort WSGH Brooklyn. WKBO City, Ill ' 5000 (Also 22.3 meters. 1000 watts) N. Y ' 227 00 WKBP battle Creek. Mich... 213 50 WMBJ Moneasen, Penna '232 50 WS I X Spring0eld, Tenn 250 150 W KB New York, N. Y 919 500 WMBL Lakeland, Fla 2.29 100 WPAP see WQAO WSKC ]lay City. Mich 273 250 WKBS Gnlesl,ulrg. Ill. 217 100 WMBM Memphis, Tenn 210 10 WPCC ('hirage,. Ill . 224 500 WSM Nashville, Tenn 337 5000 W KBT New Orlons. La 252 50 W MBO Auburn. N. Y 220 10(1 WPCH thew York, N. Y..... 326 500 WSMB New Orleans. La 297 750 WKBV Itrookvilc. Ind 217 100 WMBQ Brooklyn. N. Y. 204 100 WPEP Waukegan. Ill 216 250 WSMK Dayton, Ohio 297 200 W KB W Amherst. N. Y 217 5000 W MER Tampa, Fla 252 100 WPG Atlantic City, N. J.... 273 5000 WSPD Toledo. Ohio 40 250 WKBZ Ludington, Mich .... 200 15 WMBS Lemoyne, Pt 231 250 WP RC Harrisburg. Pa 210 100 WSRO Middletown, Ohio .... 236 100 500 WKDR tKenosha, WIR 243 15 WMBW Youngstown, Ohio.... 214 50 WPSC State('ollege.Pa.(day) 300 W SSH Poston. Mum . 288 100 W KEN Amherst. N. Y. 91)1 250 W MC Memphis. Tenet 517 50n WPS W Philadelphia. Pa 207 WSU I Iowa City. Ia. (day) .. 976 500 W KJC lane :weer. Pa 252 50 WMCA }New York. N. Y.... 370 500 WPTF RUlcieh. N.0 545 500 WS UN St. Petersburg, Fitt.... 517 751, W KRC CinrinnaU, Ohio 216 500 WMCO Saginaw, Mich...... 219 250 WPUB New York. N. Y 236 son WSVS Pufalo. N. Y 50 WHY Oklahoma City, Okla 255 150 W MES Mutton, Mass 211 50 W QAM Miami. Fla 134 750 WSYR Syracuse. N.Y 225 500 WLAC -WDAD Nashville, Tenn. 225 1000 WMPC Lapeer, Mich 231 30 WOAN Seranton. Pa 231 250 WTAD .11 ney. Ill 226 250 W LAP Louisville. Ky 265 :t0 WMRJ Jamaica, N. Y 207 10 WQAO -WPAP tcllffslde, N. J...395 500 WTAG Worcester, Mass 517 250 WLB Mlnneapolls, Minn... . 246 500 WN AC- WB IS Boston, Mass 461 500 WC/BA Tampa. Fla 238 250 WTAM Cleveland. Ohio +400 3500 WLBC Muncie. 210 50 Norman. Okla 240 500 WQBC Utica, Miss (day) 216 100 Ind WNAD WTA Q Eau Claire, WLBF Kansas City, Mo 210 50 WNAL Omaha. Neb 258 2500 W QBJ Cinrksbure. W. Va... 240 65 Wis...... 254 500 W LB Petersburg. Va 214 100 (Also 105 meters. 50 watts) WQJ rldragn. TII 447 500 WTAR-WPOR Norfolk, Va 236 500 WLBH Farmingdale, N. Y.... 232 30 WNAT Philadelphia. Pa 255 101 WRAF Laporte. Iod...... 208 100 WTAS tlatavla, Ill 275 500 1 14:ví WLB \acnona. III .... 2:t8 250 W NAX Yankton, S. D. (day) . 275 100(1 WRAH I'rm -klem' . R. T...... 200 250 W TA W College Station, Tex 4134 500 WLBL }Stevens Point. \t tsC.. 333 1000 WNBA Forest Park, Ill '05 200 (ibis short- wave transmitter) WTA X Streator. Ill 248 50 W LB Cambridge. Mass..... 231 50 WNBF Endicott, N. Y. 07 Si) WRAK WLBN Chicago, Ill. (portable) 201 50 WNBH New Bedford, Mast 248 251) Tìsranahl, Mlch. 283 50 WTAZ Richmond. Va 220 15 W LBO Galesburg. Ill .. .. 217 100 WNBJ Knoxville. Tenn...... 207 Si) WRAM Galesburg, III 248 50 WTFF Mt.. Vernon Hills, Va 203 10.000 WLBQ Atwood. Ill 219 25 WNBL Bloomington. III 200 15 WRAW Reading, "t 238 100 WTFI Toccoa, Ga...... 210 250 WLBR Ttoekford. III 2245 15 WNBO Washington. Pa 21t IS WRAX Philadelphia. Pa...... 213 250 WTHS Atlanta, Ga 227 200 WLRT 15 Crown Peint., Ind..... 215 50 WNBQ Rochester. N. Y 2115 WRBC Val Irmo Ind. 938 250 WTIC Hartford. Conn 535 500 W LBV Mnnslleld. Ohio. 207 50 W N BR Memphis, Tenn 229 101) W RC Washington.htnhin gt n n, D. C.... 483 500 WTMJ Milwaukee. Wls 294 1000 W LB W Oil City, Pa...... 291 500 WNBT Elgin, Ill. (time lias.) . 35.5 500 250 W LB long Island City. N. V. 201 250 WNBW Carbondale. Pa. 200 W O Raleigh, C 217 WTRL Midland Park, N. J 207 15 WLBY Iron NImintaln. Mich. 210 50 WNBX Springfield. Vt... 2-12 10 WREC ¡Memphis, Tenn 250 fill WWAE Chicago, Ill 227 50C WLBZ Dover- Foxeroft, Me.. 203 250 WNBZ Saranac Lake, N. Y... 232. 10 WREN Lawrence. Kan 254 750 W WI Detroit. Mich 353 1000 WLCI Ithaca. N. Y 218 50 WNJ Newark, N I 268 250 W RES Qnlney, Mass...... 217 50 W W L New Orleans. ta 246 500 W 216 50 LE Lexington, Mass (Has short-wave transmitter) W R 150 W W NC Asheville. N. C 297 1000 WLIB Sc WGN WNOX 265 1000 HF Nashington.D.C.(day) 322 r Knoxville, Tenn W W 200 100 W LIT Philadelphia. Pa 405 .501) WNRC Greensboro, N. O..... 224 2.50 WRHM tMlnnm po Ifs, Mitin... 2R1 1000 RL tWoo(Iside. N. Y WLOE Chelsea, Mast ?II 100 WNYC New York. N. l'...... 526 500 WRK Hamilton. Ont 205 100 WWVA Wheeling, W. Va. 517 250 *Allowed higher daylight plower. Standard or constant-frequency transmission. }Remote Control.

LIST OF CANADIAN BROADCAST CALLS CFAC Calgary. Alta 435 500 CHGS Summerslde, P. E. I.. 265 25 CJOC Lethbridge. Alta 268 50 CHOC Hamilton, Ont 341 100 CFCA Toronto, Ont 357 500 CHIC Toronto. Ont 357 500 Cl OR Sea Island. B. C 291 50 CKOW Srarbnro. Ont 291 500 Alontreal, Que 411 1050 CH MA 517 250 CJRM Moose Jaw. Sask 297 500 CKPC Preston. Ont. 248 0 CFCF 500 Edmonton. Alta CFCH Iroquois Falls, Ont 250 CHML Mt. Hamilton. Ont 311 511 CJSC Toronto. Ont 957 500 CKPR Mldlnml. Ont 268 58 CFCN t':lgar>'. Alta 435 ]fiá0 C HNC Toronto, Ont 357 ron CJ WC Saskatoon, Sask... 330 250 C KSH St.. Hyacinthe. Que 312 50 CFCQ Vancouver. It. C 411 IO CHNS Halifax, N.. 392 1(01 CJVC Searboro. Ont 291 500 C KSM Toronto. Ont 291 1000 CFCT Victoria. B. C 476 250 CHPC Vancouver. 11. C 411 1000 CKAC Montreal, Que 411 1200 CKUA Edmonton, Alta 517 500 CFCY Charlottetown, P.E.L 312 100 CHRC Quebec, Quo '11 5 CKCD Vancouver. B. C 411 1000 CKWX Vancouver, B. C 411 50 50 CFGC Brant font, Ont 297 50 C MSC Unity. Sask 265 C KC I Quebec. Que 141 21 C K Y Winnipeg, Man 944 500 922 500 CFJC K ainloops. II. C 265 CHUC Saskatoon. Risk 330 5án C KC K Regina, Sask.. 312 501 CNRA Moncton. N. Il CFLC rresentt. Ont 207 50 CH WC Regina, Sask 912 15 CKCL Toronto. Ont 957 509 CNRC Calgary. Alta...... 435 500 CFMC Kingston. Ont 268 C H W K Chllliwaek. It. C 24.4 5 CKCO Ottawa Ont 435 100 CLARE Edmonton. Alta 517 500 CFNB Fredericton. N. B 245 CH YC Montreal, Quo 411 7.50 CKCR St. George Ont 25S 25 CNRM Montreal. Otte 411 1650 CFQC Saskatoon. Sask 330 SOO Cl BC Toronto. Ont 291 -357 Sun C KCV Quebec Que 941 50 CNRO Ottawa. Ont 435 500 CFRB 291 1001 CJBR Regina, Soak 912 500 CKCX Toronto Ont 291 500 CNRQ (Amber, One 941 50 CFRC Kingston, Ont. 265 5(10 C ICA Edmonton. Alta 517 500 CKFC Vancouver. B. C. 411 50 CNRR Regina. Sask 112 500 C 411 CFTC Burnaby. ß. 501 Cl CI Calgary Alt 1 415 250 CKGW lnwmanvllle Ont 312 5000 CNRS Saskatoon. Sisk...... 330 500 CHCA Calgary. Alta 435 250 Ont 157 500 CHCS Hamilton, Ont 341 In CJCR Red Deer. Alta...... 357 1000 C KLC Red Deer. Alta 957 1000 CNRT Toronto. CHCT Red Deer. Alta 357 loon CJGC Landon. Ont 110 500 C KMC Cnb':It, Ont 245 5 CNRV Vancouver, 13. C 291 500 CHC Y Edmonton. Alta 517 250 CJGX Yorkton, Sask 476 500 CKNC Toronto, Ont 357 500 CNRW Winnipeg. Man 384 500

www.americanradiohistory.com 11-48 Radio News for April, 1928

MOVED adïo News

, ,,`` 7 a¡- R E ^' Or r,.ilf oratorie Ri 1>IO ma nfuctrrcrs are invited to send to RADIO NEws LABORATORIES rnents. Vo "write-ups" sent by manufacturers are published in there pages, snmplcs cf their products for test. It does not matter whether or not and only apparatus which tas been tested in the Laboratories and found of they advertise in RADIO NEWS, the RADIO NEws LABORATORIES being all indc- mechanical and electrical construction is given a certificate. As the sert'- peudent organization, with the improvement of radio apparatus as its aim. of the RADIO NEws LABORATORIES is free to all manufacture's, whethervice If, after being tested, the instruments submitted prole to be built according they are advertisers or not, it is necessary that all goods to be tested be for - to nnodert radio engineering practice, they will each be awarded a certificate warded prepaid, otherwise they canot be accepted. Apparatus ready for, or of merit; and that apparatus u-hiel: embodies navel, as well as meritorious already on, the market will be tested for tnan fact:rers free of charge. Appa- features in design and operation, will be described it this department, or in ratus in process of development will be tested at a charte of $2.00 per hour the "b1'hat New in Radio' department, as its news value and general interest required to do the work. Address all communications and all parcels to RADIO for our renders shall deserve. If the apparatus does not pass the Laboratory NEws LABORATORIES, 230 Fifth :ItellIte, .\-eta York City. tests, it will be returned to the manufacturer with suggestions for improve-

BINDING POSTS AWARDED TILE RADIO NEWS VERNIER DIAL of two power tubes of the UN -210 LABORATORIES type with filament Of the five shown here, No. 2 con- CERTIFICATE The tuning dial shown is of very current of 2A OF MERIT NO. 2264. amperes sists of two separate part: a round fine mechanical workmanship. Its at 7A volts and makes pos- knob. Inside this frame is 3A inches in diameter and sible the addition cf a power am- base and a knurled PHONE TIP knob slides a threaded cylindrical made of black molded bakelite. The The phone tips shown are of the nut, into which fits the screw which dial proper is 3/ inches in diameter spring -operated type. Each consists attaches to the base of the and calibrated from 0 to 200, around panel. of a sliding knurled sleeve and the The nut is held in position by a its entire circumference. The in- short, but strong spring. To attach dicator is of the hair -line type and a lead to this binding post, the knob has a vernier calibration which per- may be either completely unscrewed mits reading up to 1 /10 of a divi- or simply pulled out with the fingers. sion. This dial has two knobs; one in the center for rough adjustment, and a smaller one at the lower end of the dial for controlling the re- duction gear, which has a very high ratio, namely 260:1. By pulling the little knob upwards, this may be plifier to the "B" supply unit. This transformer is rugged and -s disconnected, and the larger knob compact and in the center can be used. A four is sealed in a heavy japanned inch handle the operation iron shell. tip proper. The par'. permits of the tip of the reduction gear at a distance passing through the sleeve is flat, which prevents body- capacity, as far AWARDED TILE 1tADIO NEWS and is provided LABORATORIES at its end with a as is of German manu- CERTIFICATE No.2 No.3 possible. It MERIT NO. hole for the phone cord. This cord facture OF 2271. No. 3 is similar in construction to is tightened by the pressure of the No. 2, from which it differs slightly sleeve, which is operated by a small CONDENSER in that the sliding threaded nut is spring device. The variable condenser shorn is somewhat longer and passes through of the one -hole- mounting low -loss The top of the knurled knob. To op- AWARDED TI -IE RADIO NEWS type. The plates of the stator and erate this binding post, the knob is LABORATORIES CERTIFICATE rotor are of such shape that the held between the hides and middle OF MERIT NO. 2265. straight -line characteristic of this fingers while the thumb is pressed on condenser is of neither the fre- the top of the sliding nut. No. 4 JACK SWITCH quency, capacity, nor wavelength has a spring -operated hexagonal The jack switch shown is of the type; but it is a combination of all sleeve and is provided with two single -pole double -throw type, and three. being nevertheless very close holes; one approximately 5/32 -inch AWARDED THE RADIO NE \VS to the S.L.F. variation rate. It is LABORATORIES CERTIFICATE of good electrical and mechanical OF MERIT NO. 2270. design; the nmkc is German. POWER TRANSFORMER ff ¡ This power -unit transformer is de- especially suitable for use as a se- signed to be used in "B" power - lector switch for long and short supply units, operating from the aerials. It is compact and of ex- 110 -volt 60 -cycle house -lighting line, cellent construction. The nickel - and using a half-wave rectifier tube plated brass frame is insulated from of the UX -281 or UX -216B type. the contact springs, which are made It has three secondary windings; of phosphor bronze. These springs one, which supplies 110 milliamperes No. 5 No. 4 in diameter for ordinary leads, and AWARDED THE RADIO NE\Fn a smaller one used exclusively for LABORATORIES CERTIFICATE telephone tips. No. 5 is designed to OF MERIT NO. 2272. be used only with telephone tips. I1, accordance with the new editorial policy which RADIO These four types of binding posts are NEws has elsewhere announced, the names of the manu- EXPONENTIAL HORNS made of nickel -plated brass with a facturers or distributors of the apparatus and components The larger loud -speaker horn fine finish, and are very satisfactory described in this page will no longer be printed here. Readers in operation. who desire to know the names and addresses of the manufac- AWARDED TIIE RADIO NEWS turers of any articles described here, or whether any given LABORATORIES CERTIFICATE type of radio material made by a certain manufacturer has OF MERIT NO. 2263. been tested and certified as meritorious by the RADIO NEws No. 1 resembles in construction LABORATORIES, may obtain this information by sending a spe- No. 2, bnt has its knob molded in cific inquiry with a stamped and self -addressed envelope to the `I iWant to Know" department of Ram NEws, 230 Fifth Avenue, New York City. Inquiries as to the comparative merit of two or snore articles, which are both of approved quality, cannot be answered, even confidentially._

shown here has a coiled air cham- ber of the exponential type, is made insure a perfect contact and are at a maximum voltage of 750, is of compressed woodpulp and ap- No. 1 operated by a quarter -turn of a tapped at 350 volts for use with proximately 90 inches long; its rect- bakelite. Its threaded base is like- small metal knob of attractive de- a rectifier of the 216B type. An- angular bell is 18 x 24 inches. This wise molded in a bakelite nameplate. sign. other winding supplies 1.25 am- horn has a low cut -off frequency, and This binding post is very neat in AWARDED THE RADIO NEWS peres at 7A volts for heating the affords brilliant reproduction when appearance and satisfactory in opera- LABORATORIES CERTIFICATE filament of the rectifier. A third. used with a good speaker trait. The tion. OF MERIT NO. 2269, which is centertapped, takes care depth of this assembly is approxi

www.americanradiohistory.com Radio Ncws for April, 1928 1149 mutely 14 inches and its compact- AWARDED TIIE RADIO NEWS with a powerful unit, were excep- HIGH -RESISTANCE ness adapts it for inclusion in any LABORATORIES CERTIFICATE tionally good; particularly remark- POTENTIOMETER of a great number of radio cabinets. OF MERIT NOS. 2276 -2277. able was the response to the lower instrument is a high-resist- musical notes. This A \\'.\Rl)ED TILE RADIO NEWS ance potentiometer, using as a re- LABOR. \TOR1 ES CERTIFICATE CONE SPEAKER AWARDED TIIE RADIO NEWS OF MERIT NO. 2273. 'fhe loud speaker shown is of the LABORATORIES CERTIFICATE This speaker horn, of the same double -cone type, and uses a 24- OF MERIT NO. 2281. make as that shown above, but much inch diaphragm of parchment-paper, having a beautiful leather finish. smaller, is also of the coiled type POWER TRANSFORMER and made of compressed wood -pulp. The unit is of the balanced -armature interesting construc- The power transformer shown is Its air column is approximately but type, and of "- shaped intended for use in units supply- 30 inches long; nevertheless during tion. Its laminated "U pole pieces, made of silicon steel, ing the required "A.B.C." power to are cast into the aluminum frame. radio receivers having in series up sistance element a paper strip coated ,\ heavy horseshoe permanent mag- with graphite. The contact between net, which has one side *inch longer the movable arm and the resistance than the other, is held in position strip is effected by means of a rol- with regard to the pole pieces by set ler, which insures a smooth and a screws in the aluminum frame; so good contact and does not wear out that drilling the magnet is not re- the resistance element. This poten- quired. The two coils, which are of tiometer is of the one -hole mounting elliptical section, are relatively large type and has a very neat housing, and are clamped into the pole pieces; made of nickel -plated brass, which two special holes in the frame allow contributes to perfect cooling. easy mounting of this unit on the AWARDED 'lIlE RADIO NEWS loud- speaker frame. The tone quali- LABORA'T'ORIES CERTIFICATE OF MERIT NO. 2286. to eight tubes of the 201A type, and using in the last stage power tubes of the UX -171 or UN -112 type. It ANTENNA COUPLER operates front the 110-volt, 50 -60 the tests, satisfactory reproduction cycle house line, and ttses a 350- The basket-weave coil shown is of music and speech was obtained milliampere full -wave rectifier. Two an antenna coupler of the auto- trans- from it, in connection with a good center -tapped secondary windings former type, with an inductance loud -speaker unit, and it may be in- supply 400 milliamperes at 300 volts corporated in radio receivers where on either side for the rectifier, and relatively little space is available. one ampere at 5 volts for the fila- AWARDED THE RADIO NEWS ments of the power tubes. This I.AfORATORIES CERTIFICATE transformer is of sturdy construction OF MERIT NO. 2274. and is housed in a strong metal case having a black crystalline finish. Y .` FILAMENT BALLAST AWARDED THE RADIO NEWS LABORATORIES CERTIFICATE The shown is intended resistor tics of this speaker are excellent; OF MERIT NO. 2282. for use in with the filament series the reproduction lias naturalness and of a screen -grid (type 222) vacuum great volume. tube when operated on a 6 -volt value of approximately' 170 micro - . \ \\'ARDED'THE RADIO NEWS HEAVY DOUBLE CHOKE resistance is enclosed in a casing storage battery. Its LABORATORIES CERTIFICATE The double choke shown may be henries. It of compressed cardboard with tips, OF MERIT NO. 2278. used in the filter systems of power- the corresponding ends supply units operating on 50.60- connected to of the coil. This device is of Ger- CONE SPEAKER man manufacture. The speaker shown is a reproducer AWARDED TIIE RADIO NEV'S of the free -edge cone type, with a LABORATORIES CERTIFICATE changes automatically with and takes paper diaphragm inches in diam- Il I IF MERIT NO. 2287. care of variations in the voltage of eter. It has a unit of floating- the storage battery, and insures an armature type, which is equipped An iron approximately- constant value of the with an adjusting screw. LOUD SPEAKER current flow through the filament. housing of pleasing design, in brown It may be used with any vacuum crystalline finish, encases the unit The cotte speaker shown is of the uses a unit of tube of a type requiring 132 milli- free -edge type, and amperes at 3.3 volts and operating the balanced -armature type. The 14 diameter from a 6 -volt storage battery. paper cone is inches in :nul is housed, together with the AWARDED '1'1IE RADIO NEWS cycle . when the current does \.C., unit, in a beautiful metal casing, ft1RA'l'oR1 ES CERTIFICATE not exceed 400 milliamperes. The 'IF having a golden -brown crystalline \IEItIT NO. 2275. windings of the choke are connected finish. This instrument has been to three outgoing leads. The ohmic found a very good reproducer of resistance of is, approxi- POWER each coil munie and speech. "B" UNIT mately. 106 ohms and its inductance, The "B" power unit shown oper- approximately, 10 henries. This ates from the 110- 125 -volt, 50.60 - double choke is sealed in a heavy cycle house- lighting line, and uses sheet-iron container. an 85- milliampere full -wave tube as A \\'Ali DED THE RADIO NEWS rectifier; five binding costs supply CERTIFICATE taps for the necessary voltages LABORATORIES re- OF MERIT NO. 2283. quired to operate the average com- mercial radio receiver. The unit has a maximum output of approxi- CONE SPEAKER mately 50 milliamperes at 140 volts. with the cone. reproducing The double -cone loud speaker properties of this >ps :tkcr, with re- shown has a driving unit of the gard both to quality and to volume, balanced- armature type. 'l'hc repro- are very satisfactory. ducing cone is 20 inches ins diam- AWARDED TIIE RADIO NEWS eter and very handsomely decorated; LABORATORIES CERTIFICATE the base of the speaker is of cast OF MERIT NO. 2279. brass and has a very pleasing de- AWARDED TIIE RADIO NEWS EXPONENTIAL HORN LABORATOIt I ES CERTI l'IC. \'rF The loud- speaker horn shown is OF MERIT NO. 2288. of the exponential type and made of impregnated fabric: the effective length of its air column is approxi- :\ selector switch, located INTERFERENCE ELIMINATOR on the mately 100 inches, and its bell sec- output panel and operated by a plug, The filter device shown eliminates tion is 18 x 2.1 inches. This coiled is provided to take care of the cur- completely, or reduces to a great ex- horn bps n depth of approximately rent demands of different radio re- tent, the radio interference date to ceivers; it can be used also to com- motors up to five horse power, when pensate the different line voltages. inserted between the motor and the Two extra binding posts on the power line; it consists of two choke panel are connected to an automatic coils and two condensers of .05 -mf. double -pole relay switch built into each. The two coils are inductively the unit; this switch is operated l.y coupled and have a common core the filament current and controlled made of iron strips: the P.C. re- from the filament switch of the re- sign. The performance of this in- sistance of each coil is very low, ceiver. It requires approximately strument in reproduction of both approximately .037 ohms. Coils and 600 milliamperes to operate and has music and speech has been found to condensers are housed in a heavy a resistance of approximately 0.21 13 inches a ul may be very conveni- be satisfactory. iron case, with several holes on its ohms. The entire unit is enclosed ently instal cd in many radio cabi- AWARDED THE RADIO NEWS sides to permit good air circulation in a molded hard rubber case of nets. The results, obtained when LABORATORIES CERTIFICATE and insure effective cooling. attractive mahogany finish. this horn was tested in cnnneet,nn OF MERIT NO. 2284. (Continued on poor 1191)

www.americanradiohistory.com 11:0 Radio News for April, 1928

THE INTERPLANETARY RECEIVER YOU TELL 'EM PEP UP YOUR BATTERY Astronomical note from In the Lake County (Il- A new method of remov- the New Harm Sunday linois) Register of Jan. 11 ing battery oxide is men- we have titis very de- Register of Dec. 18: frank tioned in the 11 CFL Radio "Panel template for drill- scription of a well -known //Ñ Magazine, (Vol. I, No, 2): ing METEOR holes, bind- manufacturer's sets: "The "The green oxide may be ing posts and variable re- addition of the new plant removal b touring sistances." If you have to will permit a larger manu- warm WEATHER slowly wait until some night when facture of complete radio over the surface of the bat- meteors are falling thick sets 1- MAUDLIN AND tery." Mike of the Inves- and fast before you can get SOMETIMES WORSE." tigation Dept. is now on holes in your panel, we We are always for truth in his way to Washington to would advise, "Build some advertising and news; but m get some warm weather other set." this seems like an overdose. front the Weather Bureau. Contributed by Contributed by He's having a hot time ( ?). H. Vaftal. E. C. Dymond. Contributed by R. J. Haase. THAT BLASTING STUDIO PAGE MR. WEBSTER In Crosley's advertise- WHAT PRICE EUGENICS? Station 1Y.\. Aucklad. ment in Radio 'News, Feb- must put some strong stuff ruary, 1928, a Commenting on a new on the air, according to new adject- REXTRAORDINARYI type of antenna, the Radio ive is discovered HER the K. Z. Record that ONY KNOW! World of Dec. 31 says it AR3AN Radio of smacks strongly of Elinor $B3ve ONLY Dec. 23: "Mr. Fletcher Glynn: "The new is "so simple a $4 child insists on on his can put it up." With all 00 carrying \fusicone is a type I) radio work. 'I love it.' he TRAORDIN.\RY as its this eugenics and compan- says. So do his nephews companions ionate- marriage stuff stir- and PIECES." If you see and promises ring up the country, you satisfaction. . . a man with an arm or leg great ." At cant be sure of anything last a loud speaker with missing you'll know he's sex appeal! Boys, remem- these days. $4 is a low been tuned in on 15.. \. But ber the female price for a healthy child; like it. of the spe- but the trouble isn't the they cies is more deadly. . Contributed by initial cost -it's the upkeep.. W. Satterlv Contributed by Contributed by (New Zealand) L. If Bat-tin. R. Calvaechi.

LADY LUCK, THEIR PATRONESS IF you happen to see any humorous mis- AFTER YOU, MY DEAR GASTON Interesting item from the prints in the press we shall be glad to Influence of the Book of Cincinnati Enquirer of Jan. have you clip them out and send to us. Etiquette upon electric phe- 8: "For some time FW KH No RADIOTIC will be accepted unless the AFTER nomena related in the Ra- lias been styling itself as printed original giving the name of the YUN! dio World of January 21: 'the SUPERSTITION of newspaper or magazine is submitted, with "The alternating current the South.'" We were date and page on which it appeared. We does not flow through the well aware that the South will pay $1.00 for each RADIOTIC ac- condenser. It BO\ \'S in is the land of the rabbit's cepted and printed here. A few humorous and out of the condenser." foot, horseshoe, conjures lines from each correspondent should ac- We should, indeed, be able and other things smacking company each RADIOTIC. The most hu- fo extract the height of of the supernatural; but morous ones will be printed. Address all harmony from radio sets to this is a new one on us. RADIOTICS - - operated by so considerate Where's it worn! Editor, a medium. Contributed by RADIOTIC DEPARTMENT, Contributed by Roy J..Saz.ycr. c/o Radio News. IP. S. Rosenik. PRODIGIOUS PORTABILITY IS THIS FADING? FOOD FOR THOUGHT Exacting require- Why you lost that sta- Television is with us, and ments for the set con- tion the other night is re- also other things reported a VT IN A FEW MORE BEANS1 structor in prize compe- vealed in the Chelsea. Mass. RADIO WAVES t in the News Sentinel, of ZWILLYA tition sponsored by the Record of Dec. 30: "It is CHEAP TO DAY. Fort Wayne, Ind., on Jan. South African il'irelcss 14: "Light BEANS Take é alleged by the police that - ae, B'eekly, of Dec. 14: 'The the boys stole 643 pounds Pace of Sound Wave in COMPACTNESS and of RADIATION, valued Ordinary Radio." Soon weight must he reduced to at $20 front I'hilip Lewis' in old New England, in the a MINIMUM." Much in- junk shop." Our guess is heart of the Bean Belt, the genuity was required by that the junk man collects good housewives will dis- these terms: but the prob- worn out radio waves and card their ovens on Satur- &V5 lem has at last been solved peddles them to stations day and use radio to get III by a gas -filled cabinet. dissatisfied with their wave- the Sunday breakfast. I4 Contributed by length allocations. Contributed by Edwin Potter. Contributed by D. R. Baker. (So. Africa) Don Emery. FUEL HELP FOR THE FARMERS EXPENSIVE DUCK, MEN, HERE THEY COME A burning question is Advertisement found in In the Chicago American found in an advertisement the Toronto Daily of of Dec. 24 we see this in- Star FOR THE LOV in the Portland Oregon Jan. 16th: "II ADIO WBBR teresting piete of informa- OMINE WHY Not Dairy Journal of Jan. 20: FT-1TION STABLE and tubes, prao- tion: "These stations will BURN COAL? S9a0 brand new 8 -tube tically new, real snap.' try out 200 -meter broad- Red iola and Brunswick eE0 -A-I, No, Mirandy, I ain't agoni' casting next week: \'ORI) Hlf \ Panatrope COMBUSTION J.ra to get' outa bed this cold using 5000 watts and \VB- Mike of the I. D. mornin'. Let that gol- _- :BR 1000 ?l'ATTS." There informs us that coal is still durned radio feed the stock. is no doubt in our mind rather expensive but, hon- Waddya think I paid that - that WBIIR would cover estly, we would rather hunt \sl,, agent all that money for, quite a stretch if these coal than stuff that costs 1pI Qb;yr if I have to get up and do matts were rubber. We'll anything like that men- Z., /i the chores? No. siree. quit. .. thine,' in the advertisement. Contributed by Contributed by Contributed by IL. Garlick. Osen McArille. J. L. S. Snead. HAIL, HAIL, THE GANG'S ALL HEREI FOR THE RURAL RECEIVER TWENTY -FOUR VOTES FOR Volsteadian motif in re- Pastoral gesture from Forerunner of the coming - in ceiver design, mentioned CONE the Chicago Evening Post political campaign men- the Radio World of Dec. GOT THEÉ STIOSTATION of Tau. 5: "A quarter -inch tioned in the Radio World 3: "A friction drive RUM NOW. GRASS shaft is provided of Dec. 31: "IRE Conven- is employed.... this in so that the condenser may tion Here Soon." We have connection with a gang con. be used as any ordinary filially persuaded Mike of denser. We wish the manu- variable condenser." When the Investigation Dept. to facturers of sets to under- your set doesn't tune in a run for Generalissimo of stand that this bootleg stuff station so very well, you Broadcasting. Among his can NOT be trusted. We might look inside and see other jobs will be to find want the varnish left on if someone thoughtlessly out why tenors live. They're our set, so we'll stick to used grain or alfalfa, there- the ones that are stirring up the old dials. by clogging up the works. all the ire, Contributed by Contributed by Contributed by II'm. It iet'C. Ronald A. McNeill. L. Gcfscr.

www.americanradiohistory.com Radio Nees for April, 1928 1151

Conducted by C. W. Palmer T HIS Department is conducted for the benefit of our Radio Experimenters. We shall be glad to answer here questions for the benefit of all, but we can publish only such matter as is of sufficient interest to all. 1. This Department cannot answer more than three questions for each correspondent. Please make these questions brief; if the inquiry is concerning a circuit other than a standard, published one, delay will be prevented by enclosing a diagram and other necessary information. 2. Only one side of the sheet should be written upon; all matter should be typewritten or else written in ink. No attention paid to penciled matter. 3. Sketches, diagrams, etc., must be on separate sheets. This Department does not answer questions by mail free of charge. 4. Our Editors will be glad to answer any letter, at the rate .,f 25c. for each question. If, however, questions entail considerable research work, intricate calculations, patent research, etc., a special charge will be made. Before we answer such questions, correspondents will be informed as to the price charge.

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WHAT IS DETECTION? considerable distance, and by this means we might, very feeble little wave which we thus receive; for instance, send a message. Disregarding the we want to put in motion in one channel a much (2272) Mr. R. J. Wentworth, of St. Louis, Mo., complexities which are presented by the very in- larger amount of water. Iiere is where the "am- writes: tricate sounds of music and speech, let us con- plifying" action comes in. A radio tube is truly (Q.) "Will you explain how crystals and vacu- centrate on the idea of sending a succession of a "valve," as they call it in Europe; a small volt- um tubes operate, when used for 'detecting' radio impulses, in the form of waves, which are com- age applied to its grid, under certain conditions, signals ?" parable to the dots -and- dashes which puzzle, and turns on and off the current from the 'B" battery, A. 'l'he crystal detector, which was very popu- occasionally annoy, the ordinary radio fan. which is much greater in its electrical effect. lar several years ago, and is still used in a very To illustrate the action of a tube, we have what large number, if not a majority, of the radio A Hydraulic Comparison is known as its "characteristic curve." Without If we dip out and pour back a bucketful or so explaining too technically the action it represents at more or less regular intervals from and into (see the department, "The Radio Beginner," in the body of water which is to be our medium of this issue) this curve indicates the amount of communication, we will set up waves; that is to "plate current" which the tube passes, for any say, we cause the water to rise and fall in rapid given amount of voltage difference between its succession, for a considerable distance from our filament and the grid and with a fixed value of scene of operation. This is not a forward motion plate voltage. The plate current is proportioned of the water, for the bucketful we pour in stays to the height of any given point on the curve just above on near us for a considerable length of time; it is the point the scale indicating the corre- a backward- and -forward, up-and-down motion, cor- sponding grid voltage. At the bottom we have shown responding somewhat to that curve representing the effect of a typical "train" of radio "voltage changes that we picture when we talk waves on the grid voltage. and in the horizontal curve the corresponding of a "radio wave." We can put a small float "wave" in the plate cir- on the surface of the water, at the point where cuit of current which can he used to actuate the we wish to receive the message carried on these diaphragm of a telephone (See Fig. Q. 2272 C.) waves; or let us make a little dam with its top Returning to our water analogy, the simple at the exact water level, shown 227211 rectifier, such as the crystal, cannot put into the as in Fig. Q. telephones at (1) and (2). When the "trough" of a wave any more energy than it receives -less comes along, no water will spill over; but when in fact, as current is used up in overcoming its the "crest" arrives, it will break over the top resistance. Just so our little dam in Fig. Q. 227211 (2) of our little dam. This action we may compare must surround a depression kept lower to that of our crystal detector, which responds than the water level, so that the incoming wave can spill to the radio wave by passing only the half of it into it. which is "above the line;" that is, the impulse in The Hydraulic Amplifier one direction only. But we can use the rise and fall of a float But we desire to get something more than the on the waves to operate a gate and control the

Three radio circuits using common defection method.! 1, crystal; 2, plate- current or "bot- tom -bend" rectification,. with negative grid bias; 3, grid rectification with positive bias regulated by grid leak and condenser.

receivers outside of the United States, has the peculiar property of offering a higher resistance to electric currents passing through it one way than it does to those passing in the opposite direc- tion. The radio -frequency alternating current, which we call the signal, comes from the aerial (or possibly through an 12.F. amplifier) and tries to pass through the crystal, first in one direction, and then in the other; but its flow is practically confined to one way, because of the increased resistance offered to the current whenever it is reversed. Thus, only one -half of the incoming current passes through the headphones in the simple crystal -detector circuit shown by the dia- vrant in Fig. 2272A at (I). When we use the well -known three -element vacuum tithe as a detector, we have our choice of two methods of detecting or "rectifying" radio signals; they are called "plate rectification" and "grid rectification." While the first is more easy to explain diagrammatically, the second is more commonly used. In addition to its detecting effect, the tube introduces also the action of "amplifica- tion." A rather simple analogy may serve to convey the idea, though not with complete details, Above is a comparison of radio detection with that of water waves. In I and 2 we have simple "half - in a form easier to comprehend. wave" rectification; only the top half of the wave spills over the don. waves In 3, 4 and 5, the float repre- We may compare the radio signal to sents the tube grid, and the water in the aqueduct the plate current. In 6 the tank represents the grid caused by agitating water; these will travel a condenser; it discharges through the "siphon" (the grid "leak ") when the pressure becomes high enough.

www.americanradiohistory.com 1152 Radio News for April, 1928

flow of water from a higher level to a lower, as This is in contrast to the other method of de- verted into electrical alternations (1) at rates in Fig Q.2272B (3). Above our float we have tection, which is that used in most radio receivers, varying from about 30 to 5,000 per second; and an aqueduct containing a "weir," or water outlet, and which we will now describe. then allowed to modulate more powerful alterna- and a "sluice gate" regulating the flow of water. tions (2), macle at a rate of from 550,000 to This gate, when it is perfectly level, permits a Grid Rectification 1,500,000 -per second, in the case of ordinary broad- very slight amount of water to escape. It is cast stations. In the case of short-wave stations, pivoted far over to one side, so that tilting it When we refer again to Fig. Q.2272Á, at (3), the carrier -frequency alternations may be at the one way permits a great deal of water to escape; we find that the grid return has been changed from rate of 20,000,000 a second. It is evident that while tilting it the other way practically cuts off the "A -" to the "A +" filament lead, and that, each vibration of a 256 -per- second (256 cycles the flow. We connect one end of this sluice to in place of the "C" battery, we have a "grid equals "Middle C" on the piano) audio -frequency our little float. leak" and a "grid condenser" in the grid -filament \ \lien the float rises, as pictured at (4), a great circuit. This places on the grid a positive bias deal of water escapes; when it falls (5), the flow of half the value of the voltage across the fila- is practically cut off. The result is that, as the ment (when the grid is compared with the middle waves come in and lift our float, they increase point of the filament); this is usually sufficient, and decrease the flow of water, at a much higher without requiring an external application of posi- level and to a much greater amount; but that tive voltage. flow is steady and in one direction, not the back- The action when this method is used is as fol- ward-and-forward motion of waves. This is also lows: the incoming signal voltage tends to send the difference between the radio wave and the a current through the circuit, from the grid to direct -current impulse which operates our tele- the filament, and back again. But this current photo diaphragm. can flow in only one way, from the grid to the -2- filament; because of that property of the vacuum which permits electrons to travel only from s t s Plate- Current Rectification tube IV a hot element (the filament) to a cold one (the t It2/At,rsrsrs.srsrtl Returning to the electrical action, Fig. Q.2272C grid or the plate). This current flow builds up Q' shows the plate- rectification eiTect which corresponds an electric charge on the grid condenser, and to the apparatus we have just described. It de- causes the voltage on the plate of the condenser pends on the "bend" which we see at the bottom which is nearest the grid to become negative, as of the " chardcteristic curve" of our tube, and well as the grid itself. which corresponds to a limiting range of negative Whenever the radio wave reverses, it merely -4- grid voltages, varying with the type of tube. In or- stops the flow of electrons; for the space between der to keep the grid at this negative voltage, com- the filament and the grid will pass a current in pared with the filament, it is necessary to use a "C" only one way. Thus the flow front the filament battery or voltage -supply source with its positive keeps increasing the negative charges on the grid terminal connected to the "A -:" for the "A-" until they oppose the incoming signal voltage and voltage alone is not far enough below that of all overcome it. The grid leak then allows the charge -6- points on the filament. Such a "C" battery is usu- to leak off through the grid return to the filament. Q - 2272 D ally composed of several dry cells in series; or the This cycle is repeated with each train of waves, "voltage drop" between the ends of a resistor in a the grid being in the same condition at the end as power unit may be used for the purpose, (Fig. at the beginning. The resistance of the grid leak In the illustration above, 1 and 2 represent Q2272Á at 2.) must be of a suitable value, to secure smooth the broadcast A.F. modulating wave and the At the bottom of the diagram, below the bend operation, however. station carrier tease, which are combined by in the characteristic curve, we have pointed out This variation of the voltage on the grid, caused "modulation" to form the alternating signal the "voltage wave form" of the incoming radio by the incoming signal, will also produce a varia- wave shoran at 3. at .4 we hate the result of as becomes detection, a soinetuhat distorted, pulsating direct wave. If we draw a line directly upward from tion ill the plate current; the grid more negative, it decreases the flow of current from current; this is separated by suitable means any point on this curve, representing the voltage an becomes into A.F. direct-current signal impulse, 5, on tla grid at that instant (the grid negative volt- the "B" battery or power unit; and, as it and an R.F. compostent, 6, which is by-passed age or bias," plus or minus the voltage of the positive again, the flow of plate current becomes back to the filament, used for regeneration, or received signal, according as the incoming wave is normal. otherwise disposed of. at a positive or a negative stage) until it meets the It will be, perhaps, more difficult to explain characteristic curve, and then extend another line the difference between these two methods of tube horizontally to the upright scale marked "plate detection by our hydraulic -gate analogy, to the note covers the period of 5,000 alternations of current," we will get the value of the current flar- satisfaction of our readers. They would correspond the carrier wave of a 1280 -kilocycle (234.2- meter) ing between filament and plate at that instant. most closely to a readjustment of our wave- operated broadcast station; and its influence is therefore Tf, for each value of the grid voltage, we find the float, and of the point of pivoting in the sluice- spread over 5,000 successive alternations on the corresponding value of the plate current, we can gate which it opens and closes. In one method, grid of the detector tube of a radio set receiving draw the resulting wave form of the plate current- we may say, the rise of the float closes the open- a broadcast from this station. It is therefore which is all direct current. It will be seen that ing; in the other, the fall of the float closes the desirable that, so far as possible, the effects of there is present some "distortion" of the wave gate. Also, let us suppose that, to correspond the carrier -wave be eliminated entirely from the font: that is, the variations in current arè greater with the grid-rectification process, the float is in audio stages of a radio receiver; as their presence in one direction than in the other, when compared a compartment into which successive waves spill. (6) causes a "radio- frequency component," which with the variations in voltage. In the diagram each raising the float a little more, until the is a sottrce of trouble, and is combated by the use this result has been exaggerated to make it evident. water rises above an overflow level and discharges of radio -frequency chokes (the action of which through a siphon (6). was It is plain that we have in this case, not a described in this department for February). In comparing this system to radio waves, we true rectifying action, as with the crystal -but a must suppose that these waves are created in series relay or amnplifying action. will also It be noticed by the millions, in regular succession ELECTROLYTIC RECTIFIERS that, with this method, or "trains" no current flows in the with varying intervals and heights; and it is our grid circuit -unless the grid is allowed become (Q. 2.) would like to obtain some informatiot, to desire to gauge, not the height of single waves, "I positive there is no drain on the battery. about electrolytic -and "C" but the respective rapidity of the changes which rectifiers and the solutions used in them. \Vhat is the best and are made in the rate of their production and the electrolyte, what are the phos- height of their crests. This corresponds to "modu- comparative advantages of ammonium phate and ammo m borate over the usual borax lation" in radio; and the reverse process is "detection." used in aluminum -lead -type rectifiers ?" There are several differences between these two (A. 2.) In the usual home - constructed rectifier, a - PLATE - CURRENT types of tube rectification. Plate rectification does saturated solution of commercial borax ( "sodium CURVE not consume any grid current, normally; but with bilorate ") is employed. This electrolyte is suit- grid rectification there is a flow of current (drawn able in most cases; but if the borax is not entirely from the "A" battery) in the grid circuit. An- pure considerable trouble may he encountered. Am- RESULTING other difference is that the plate -current method monium phosphate or ammonium borate dissolved WAVE FORM produces the sounds in the phones by an increase in distilled watèr. is much more suitable. The GREATER ON in the plate current: the grid -current method by former is prepared by dissolving as much "pri- ONE SIDE a decrease in the plate current. The latter actu- mary" or acid ammonium phosphate as the water THAN THE OTHER ally rectifies the incoming signal in the grid cir- will take up, thus making a saturated solution. cuit, because the changing bias on the grid allows Crystals should he added until they fall to the the grid current to flow in only one direction; the bottom, and then the liquid should be filtered off 1 former rectifies the current in the plate circuit, and used. A similar procedure may be followed 111111 the borate; ti Ili because it is possible for it to flow there in one with care should be taken to procure way only. a chemically -pure "salt." O + GRID POTENTIAL The sum of the current changes, with either The ammonium -phosphate electrolyte may be al- method of detection, over a period of thousands lowed to stand idle for a long period of time with- of cycles of the radio wave, will be found to out injury. The ammonium- borate electrolyte, dur------IMPRESSED correspond very closely to the electrical modifi- ing an idle period, will increase its internal re- WAVE TRAIN" cation caused at the microphone of the broadcast sistance, which causes the voltage to drop off con- OR SIGNAL VOLTAGE station by the sounds of speech or music which were siderably. In some cases, it is necessary even to tieing broadcast. For this reason, the phones or scrape the electrodes to make the rectifier function. loud speaker in the output of a detector circuit The ammonium- borate solution reacts upon the lead Q- 2272 C will reproduce these sounds very closely. plate: thus forming "lead peroxide," which gradu- ally- falls to the bottom of the container. No such Modulation and Rectification trouble is encountered with ammonium phosphate. The "characteristic curve" of a vacuum tube is The aluminum electrode should be of the purest a diagram of the amplification it gives, and The grid -rectification method is more sensitive, metal obtainable; since any slight impurity will every student of radio should he familiar with because the effect of the small individual waves cause a "local action" which will ruin the recti- the idea represented. The "signal" in every of the signal impulses is "cumulative" in its fier. It is advisable to place a rubber tube over tube comes in as volfaae on the arid; it pots influence on the plate current, thereby producing the aluminum plate at the point where it leaves the out as current through the circuit. A plate. match greater voltage changes on the plate than solution, so that oxidization cannot take place at drawn a "characteristic curve." for given tube, 2272D. at a given plate voltage. shores what response does the plate- rectification method. See Fig. this point. may be expected from it for any given grid bias. Each audible note reproduced in radio is con- (Continued on page 11911

www.americanradiohistory.com Radio News for April, 1928 1153

www.americanradiohistory.com 1154 Radio News for April, 1918 A Novel Radio Dial Airplane SOS Saves Ships TUNING devices have assumed many odd 'r HE "SOS" has more than once of late shapes; but there is a great deal of in- called shipping to the assistance of genuity in the indicator now used on a aviators; the compliment was returned in French make of receiver. The pointer of the English Channel not long ago, when the one tuning condenser moves horizontally, pilot of a London -Paris aerial express ob- and the other vertically, across a scale; and served that a small steamer below him was their intersection shows the position of the on fire. He at once used his transmitter to station tuned in. u will be noticed that notify Croydon, England, which broadcast the alarm. It was picked up at Boulogne, France, from which port a tug at once put cAre You a out, rendered timely aid, and towed the dis- Service Man Custom Builder tressed vessel with her crew of fifteen safely Engineer Mechanic into port. Dealer Student Advance Experimenter

Are You A New Radio Gadget FROM the columns of our British con- Interested in temporary, The Wireless Trader, we re- produce the illustration of a new accessory, 1. Advanced material on electrifica- which, as its editor remarks, is long over - tion and power supply. due. The vessel is composed of baked red 2. The mathematics of radio. clay, like the ordinary flowerpot, but is 3. A monthly review that includes equipped with a handle, and filled with the from six to ten construction articles each month on the outstanding highest quality of ground, in which is em- construction developments. bedded a small copper terminal for quick connection to the "ground" terminal of the IF SO, SEE COUPON BELOW receiver. This convenience is, of course, especially designed for Tuning scale of a new French receiver, for two wavelength bands. use with portable re- RADIO ceivers; but may, sug- there are two curves across the chart of gest the makers, be ENGINEERING wavelengths. One represents the lower used as well for grow- range of European broadcast stations, prac- ing rhubarb or holly- has been published for seven hocks. (We would years exclusively for the pro- tically equivalent to our broadcast band; fessional men of the radio indus- and the tither the long-wave stations, be- suggest currants, but try and trade. It includes each tween a thousand and three thousand care must be taken month a review of important meters. that the fruit does not construction developments, to- fall from the shrub gether with some forty pages of and go astray.) As carefully selected articles on April brings pleasant technical and semi -technical and garden subjects prepared by leading The Voice of Wales outdoor engineers of the industry-ex- WELSH members of the English Parlia- clusively for RADIO ENGIN- ment have united in a demand on the 'A"'1 new "' portable "' ground, EERING. A non- biased source designed by a British in- of accurate technical information. British postmaster- general for the estab- ventor. lishment of a broadcast station in Wales devoted exclusively to programs in the weather, as a rule, there should be a con- The Editorial Staff Welsh language. It is represented that this siderable demand for this portable ground is headed by would be a great stimulus to the sale of -especially around the first of the month. Mr. M. L. Muhleman radio sets in Wales, as well as of cultural Our enterprising American manufacturers Advisory Board of Editors value. will undoubtedly be prepared to meet it. John F. Rider Zeh Bouck Harry G. Cisin James Millen A, Austin C. Lescarboura Proposed Television Set -"The Motorist's Friend" RADIO ENGINEERING IS NOT SOLD ON NEWS STANDS

RADIO ENGINEERING, Inc., 52 Vanderbilt Ave., New York, N. Y.

for 1 year f $2.00 Enclosed find 1$3.00 for 2 years subscription to RADIO ENGINEERING. Enclosed find twenty cents (20c.), for which send sample copy of RADIO EN- GINEERING.

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Town and State.. Please Check Your Classification: Dealer Manufacturer Service Man Engineer Professional Set Builder Distributor C. Anything Else

- The Bystander.

www.americanradiohistory.com Radio News for April, 1928 1155

"Try this on your piano" 1 $ 10 only Here it Is! only The Loudspeaker Sensation of 1928 If the success of any product is measured by what people say and think about it, then this newest radio product is a sensational success. of course

it's an product

Simply attach the ENSCO piano unit to your piano and the cord to your radio set--it only takes a minute - --and you have a marvelous, resonant loudspeaker. /4//). This wonderful device makes use 11I I1 t // of the perfect sound -reproducing It doesn't show -it does not qualities of the piano sound- mar the piano in any way or board. It took years to develop tPY interfere with its use as a piano. the piano to its present state of perfection, and you can now Fits any piano, grand or upright, enjoy perfect radio reproduction and works on any radio set. by using this sound -board. II =1! The reproduction is simply marvelous. The sonorous bass notes, the rolling notes of the middle register, and the thin, sharp tones of the upper treble-all perfect-and the voice sounds natural. The famous ENSCO drive mechanism -the rugged direct -drive, distortionless unit developed by Clyde J. Fitch, makes this possible. It is new, and the results will surely astound you. MANY NOVEL APPLICATIONS Musical furniture is now a reality. Imagine the dinner table, surrounded by guests, bursting forth into glorious song, a chair or bridge table telling a bedtime story, or a door or panel singing a baritone solo! All this is made possible by the ENSCO piano unit. It is made by the makers of the famous ENSCO cone speaker kits under U. S. Patent No. 1630199 and others pending. The Best

. , .flt ; $10 % i You Ever Spent! 00' If you do not have a piano, use it on the table or a panel, or door. It works! Sold under money -back guarantee. You must be satisfied or your money will be refunded. Price only $10.00. Complete with 20 -foot cord. Ask your dealer or send order to our nearest office. Shipped prepaid on receipt of check or money order or C. O. D. with postage added. Price in Canada -$11.50 ENGINEERS' SERVICE COMPANY 25 CHURCH STREET 28 E. JACKSON BLVD. 331 BAY STREET NEW YORK CHICAGO. ILL. TORONTO, ONT.

www.americanradiohistory.com 1156 Radio News for April, 1928 Television Comes to the Home

(Continued from page 1100)

But there is another side to the story. meat of the wires it has been named a In studying radio reception, as we know checkerboard antenna; the sides of each it today, static, interference and fading are square being equal to half a wavelength. factors about which very little is known. All these half -wave antennas are connected These are also present in television, but in such a way that they oscillate in phase instead of being audible they are visible. and require no tuning. The Story of Not only that, but the eye is more sensitive The checkerboard antenna is not a beam to differences in shading and minute changes antenna, although all the energy is pro- of position than is the ear to differences in jected in the general direction toward which Chemistry sounds. For that reason, the study of the it is desired to transmit. The angle at FLOYD L. DARROW problems of transmission will be made much which the antenna is arranged is of great more effective by the use of television importance; for example, the one shown in apparatus. Fig. E is intended for work with San Fran- within In television "static" appears on the cisco and the left side of the illustration screen as black splotches, which momentar- is toward the west. your grasp! ily blot out the image. "Fading," such as As mentioned previously in this article, that experienced in voice transmission, re- there are still many mechanical and elec- -interesting- sults in, literally, the gradual fading out trical obstacles that must be overcome be- of the image on the lens. When the receiver fore television apparatus, such as that illus- Chemistry -Floyd L. Darrow is oscillating or "squealing" the image has trated here, can be available for ordinary has presented this subject in a home use. concise, simple manner. more contrast; i.e., the shadings and shad- But the important thing is that ows become a dead black with a correspond- it is at present a reality, and no longer Though a great deal of time merely an engineer's dream. was consumed in research work ing lightening of the "high lights." In three homes and study, the book is in such Another interesting part of radio trans- in Schenectady today television receivers a readily grasped form, it will mission, which is brought out by television, stand beside the regular broadcast receiver be nothing at all for you to is the "echo image." This condition is evi- and, although members of the families at obtain a good understanding of denced on the lens by a double image, i.e., present have to crowd a bit to see what is the subject. the appearance of a perfect secondary image coming over the air, yet the time surely is 530 PAGES -6" x 9" beside the fundamental image, and almost not far distant when they will be able to The book is beautifully and as strong. This occurs only under certain sit comfortably before the television receiver sturdily bound, with a good weather conditions and is believed to be and see with the same ease as they hear supply of interesting illus- a visible "echo" of the wave due to vertical today. trations. reflection from the electronic layer of the There certainly can be no doubt that we The price is a low figure at upper atmosphere. The echo image is usu- are on the threshold of a new era. Tele- which to gain such a complete ally displaced on the lens to a distance cor- vision has been demonstrated several times education as it affords. responding to a delay of one fifteen -hun- before in this country and abroad; but now it has been brought into the home The Story of Chemistry dredth of a second; showing that the echo in a man- wave had travelled about 124 miles and yet ner that can be readily comprehended and SPECIAL PRICE was nearly as strong as the other, which had by apparatus simple enough for the average only travelled a few miles. Obviously such man, who is not mechanically inclined, to $3.98 phenomena as this could never be detected operate. And that is a real step forward. USE COUPON BELOW by the ear. Although it is the technical man and the experimenter who have made radio what A NEW TYPE OF ANTENNA it is today, the layman-who is typical of the Experiments in the fields of television have great majority of radio enthusiasts -is the brought about a new type of antenna, which one to be pleased and catered to in the per- THE STORY OF is illustrated in Fig. E. From the arrange- fection of radio utilities. CHEMISTRY

n.endIheJrc`¡ A Novel Automatic Volume ptulr'un!`raxa'

/. Itie story of unlrihe4one wtkl,.prnddry the manifold tu n,.,drelu hart nlade h, vgd that prosperity. Control 'the 4xlp"k,e pad. dinmserim the ra.vlui,.ners tl In9ned d the Quire,nr,uvefw' the (mum Jerebp ¡fl. i (Continued from page 1131) r.iv,yd Nearly. simply und h outl Iw,u' Ik, 11d1 think beatieee a J Minh ónimrnh;rcthe Fmfield. e P rg{.vke' ' va' maJc while with a "voltage- squared" detector, the In consequence of the automatic control Fily. Chm.i,m ntvn. tp ant yet in Me t«t hmJ,e average rectified voltage is proportional to action, it becomes difficult to tune the receiv- the average total power of carrier and side- ing set accurately by car to a desired signal. bands. This last feature is worthy of men- The amplification is decreased as the re- FLOYD tion in connection with the control system; sponse to the signal is increased by tuning, L.l?ARRON since the automatic grid bias should depend and vice versa; so that the point of reson- on only the carrier amplitude, independent ance is indicated by mininnddn plate current of the modulation. in the radio- frequency amplifier. 'faking ad- CONSRAD COMPANY, INC. 230 Fifth Avenue, New York City With the circuit constants shown in Fig. I, vantage of this fact, a milliammeter (CIA, Gentlemen: I encinte 03.0$ -lease send Fig. 1) is connected in the plate circuit of me one cony of "Tile Story of Chemistry " the time constant of the circuit which con- Name nects the rectifier to the grids of the con- the first tube, to be used as a resonance indicator, and also to give an indication of .1 ddresa trol tubes is 1/40 second; so that the con- relative signal intensities. Cty. State trol system comes nearly to equilibrium in 1/20 second. This time can be reduced USE OF "B" UNIT further if necessary, but is ultimately .' a 'u i .. limited by the allowable reduction of the There is an incidental problem in supply- .rY -Ma./? the lowest audio ing the plate current to all tubes of the set .??".. 'ird;a3". r. signal modulation at frequencies. described, from a common rectifier- and -filter

www.americanradiohistory.com Radio News for April, 1.928 L157

system. ln the controlled radio -frequency amplifier tubes, when operating at low plate current, the signal carrier is modulated ap- preciably by small fluctuations in the plate voltage. Such fluctuations are caused by plate -current pulsations in the audio-fre- vER COM ES TO quency amplifier. In the presence of a carrier wave, these two effects may 0 strong j-6E-{ cooperate to generate a low -frequency oscil- IT CRYSTAL lation. This disturbance may be avoided by CLE reducing the internal output impedance of R the rectifier filter, by decreasing the ampli- fication at low frequencies in the audio - frequency amplifier, or by using separate rectifier -filter systems to supply the plate currents of the radio-and audio- frequency amplifiers, respectively.

TWO -ELEMENT RECTIFIER

HREE-ELEMENT DETECTOR.

R.F VOLTAGE. FIG. 3. The above graph shows the nearly- rectilinear proportionality between the alternating and the with a simply -rectified voltages as against the out put of a three- element detector.

The performance of the automatic CARBORUNDUMREG. U. s. PAT. STABILIZING volume control as described etut be sum- marized briefly as follows. A. maximum DETECTOR UNIT variation of signal voltage in the ratio of 1:1000, corresponding to differences in dis- tance, fading, or tuning, results in a maxi - ALL the volume you need and selectivity mum variation of the rectified carrier volt- too, when you attach this unit -but, age in the ratio of only about 1:3. This sumll variation, together with possible dif- best of all, you get clear, undistorted ferences in the degree of modulation of dif- tones natural, true, and crystal clear. ferent stations. can readily be compensated - if necessary by adjusting the manual vol Can be used on nearly all sets. control for the audio -frequency amplifier, which also determines the "volante level" e ñ"i.him I the The Complete Unit No. 32 for $3.50 for the automatic volume control. <ïï.red 'erode ]'rue m.d t.r The The Detector alone No. 30 is $1.50 The name ".\udiostat" has been selected r..N. pony tor Silicon Car. Buy from your dealer, or we for this device, by reason of its tendency to Ae. Tkle Trade The Nark letl- erela.i,e will send direct. Carborundum property the Cop Use coupon to get our Hook-lip Company Book, sent free. Niagara Falls, N. Y. / Please end free THE CARBORUNDUM COMPANY, NIAGARA FALLS, N. Y. llook -Up hook D -I 40 Non -Technical CARBORUNDUM CANADIAN CO., LTD., NIAGARA FALLS, ONT. / Name Radio Articles / Street City every month for the beginner, the layman and those who like radio from the non- State technical side. SCIENCE AND INVENTION, which can be bought at any newsstand, contains the largest and most interesting section of radio articles of any non -radio magazine GEARS in existence. All kinds -Small RADIO PANELS The most accurate made and BAKELITE -HARD RUBBER Plenty of "How to Make It" radio arti- prices reasonable. We carry a cles and plenty of simplified hook -ups for complete line of gears In stock Cut, drilled, and engraved to order. Send rough the layman and experimenter. The radio for Immediate shipment. Can sketch for estimate. Our Complete Catalog on also quote on speeial gears of Panels. Tubes and Rods -all of genuine Bake- section of SCIENCE AND INVENTION inquiries. is so good that many RADIO NEWS all kinds. Send us your lite or Hard Rubber- mailed on request. readers Write for Catalog 40 STARRETT MEG. CO. buy it solely for this feature. Chicago Stock Gear Works 105 So. Jefferson St., Chicago 520 S. GREEN STREET - - CHICAGO Radio Articles Appearing in April Science and LIGHTING FIXTURES Invention Ready to Hang Magazine Direct from the manufacturer. Completely d, including Photographs in the Home by Radio wire ma NEW 1929 CATALOG -4000 items glassware. Send for new shows the latest A-C circuits. the IICIVMSt Uras New Broadcast Station in Milan, Italy catalogue No. 29. Just Re- In nullo at startling low prices. Cet the sets duced Prices. and parts you want here. Save money. An All- Electric Six Tite best. In ¡karts. kits, entnnlete facbory- Exponential Horns Special Propouttion to Dealers. built sits and supplies. Orders filled sumo -How to Make Them day received. Write now. New Erie Fixture Supply Co.. Inc.. for free copy Radio Devices Station R, Erie. Pa. standard dtwaval.r to dealer.r, .ref hna,tCC$$,, amts. Radio Oracle -Questions and Answers BarawikCo.,129 NJefferson St., Dept..804BCitiñgoíD, Latest Radio Patents Radio Wrinkles Insure your copy reaching you each month. Subscribe to Science and Invention -$2.50 a year. Experimenter Publishing Co.. 230 Fifth Avenue, N. Y. C. .eie 1e11s1a11e11s.s1sasseas111es1ea11e.e1.mmmnus11ess1a1a1aae:amam1nmmeme

www.americanradiohistory.com 1158 Radio News for April, 1928

maintain the audible intensity at a constant It is desired to acknowledge the co- opera- value. tion of the Howard Radio Company of Chi- Attention might be called to British cago, in whose laboratory the set described BRIDGE Patent 259,664 (Western Electric Co., July was assembled. 14, 1925), in which a somewhat similar sys- 45 stations tem is presented. This other system is ap- plied to a superheterodyne receiving set, and (From an address delivered before the Institute is more involved in several respects than the of Radio Engineers, at a meeting in New York, broadcast Nov. 2. 1927, and published by permission of the system described in this paper. I. R. E.) every week Take your daily Controlling Volume in Your Receiver (Continued from page 1137) lesson now- - 500,000 ohms to one megohm can be ob- distortion results. If the distortion is to be tained. The resistor used in method B prevented, the input to the detector must should have a maximum value of about one always be kept below the overloading point. get any one of megohur. If the volume control is located ahead of In the preceding paragraphs we have dis- the detector tube, this is possible; but if the these Bridge cussed in a general way various common control is located in the audio amplifier a methods of volume control and have pointed reduction of the signal strength before de- out, to some extent, the relative advantages tection is not possible and overloading of Books to help and disadvantages of the various methods. the detector may occur. The reader should now have a good concep- The control of the output from a super- tion of their operation and characteristics. By C. heterodyne type of receiver is best accom- Wilbur Whitehead: One phase of the subject remains to be cov- plished in the intermediate- frequency ampli- Complete Auction Bridge 22.00 ered, which is whether, broadly speaking, it fier. A high resistance in series with the Auction Bridge Standards 1.50 is better for the volume control to be be- "B+" load to the intermediate- frequency Auction Bridge Summary 1.00 fore the detector (in the R.F. amplifier) or amplifier will serve very well. In many after the detector (in the audio amplifier). superheterodynes the oscillation control, By Milton C. Work: regulating the in R.F. METHOD RECOMMENDED amplification the I.F. amplifier, is used also as a volume control. Bridge Pointers and Tests $1.00 In general, it can be said that the volume Contract Bridge 1.50 be de- Owners of receiving sets equipped with Auction Bridge Complete 2.00 control should placed ahead of the tector. The signals received from local sta- poor volume controls must frequently re- tions are comparatively strong and, after sort to detuning one or more of the R.F. stages to adjust the volume properly. Such Foster's Contract Bridge 1 00 amplification in the R.F. amplifier, the volt- Ferguson's Contract Bridge .50 age is considerable. A detector tube can practice is not to be recommended, and a 100 Bridge Lessons 50 handle voltages only up to a certain value, better volume control should be installed in Practical Auction Bridge 2 00 beyond which overloading takes place and the set. Shortcut to Standard Auction Bridge 1.50 Auction Bridge (Annual Magazine) .75

Prepared by Famous Broadcasters Why Batteries are Still in Fashion 'Listeners in need no introduction For Short -Wave Receivers to Work and Whitehead. They are the most famous of Bridge Broad- MANY of us have probably wondered picked up when the aerial lead -in paralleled casters, and masters of the game. why, in the numerous diagrams ap- the house wiring, even though it might be This is a selection of their pearing in the various radio publications, separated by many feet, and how the prox- best books. of short -wave receivers, whether designed imity of an electric light was sufficient to for short-wave -broadcast or code reception, also cause this effect. Many of the plays that did not "B" batteries, rather than socket -power de- Furthermore, a stable plate current is clear up in your mind over the radio vices, are always designated as a source of vital to success in short -wave reception. The can now be studied at leisure. plate supply. That there is a good reason tickler is almost always in a state of micro - for this, however, is indicated by some metrically- critical adjustment; consequently, Whatever is to be known about interesting tests recently made. if the plate current is not stabilized and Bridge will be found in these books. In the first place, a short -wave receiver varies ever so slightly, it will cause the is almost invariably of the regenerative type, tube to spill over, thus necessitating read- These are books to fit every need and consisting of a detector and one or two justment. As the A.C. input to the power every purse. stages of audio amplification. It is de- unit is varying constantly and this varia- signed on the low -loss principle (which in tion on a smaller scale, is reflected in the Pick your books now -and be assured that your knowledge short -wave reception really means some- output of the device, the impossibility of will be coming from masters thing) and consequently is extremely sensi- maintaining a state of critical adjustment tive and must be capable of maintaining is obvious. Each book is well bound, printed in the most critical adjustments. When it is This varying voltage is a factor also in legible type, and contains anywhere used in connection with a power unit, the broadcast reception on the higher waves, from 160 to 500 pages. remaining unsuppressed A.C. hum, which and has caused a few manufacturers of "B" may be entirely unnoticed in the ordinary power units to incorporate a regulator or broadcast receiver, becomes pronounced and glow tube in their outfits. 'l'Iris glow tube Order Direct grows in intensity as the regenerative cou- has as its function the preservation of a uni- pling is tightened. In addition to this re- form current flow, but, unfortunately, its sidual A.C. hum, the alternating- current current consumption is so heavy that it can CONSRAD CO., INC. variations may also be picked up through be used only in eliminators especially de- the antenna system. Many radio fans, who signed for it; as otherwise it drags down 230 Fifth Ave., New York City possessed in the old days broadcast re- the over -all voltage, causes choke -coil core ceivers of the regenerative type, will prob- saturation, and intensifies the A.C. hum. ably recall how easily the 60 -cycle hum wns Because of the sensitivity of the short-

www.americanradiohistory.com Radio News for April, 1928 1159 wave receivers to all forms of electrical disturbance, background noise must be eliminated whenever it rests within the power of the set operator to accomplish this. Power units, when used on short -wave re- ceivers Emil highly- sensitive broadcast sets, are inherently noisy, owing to line fluctua- tions. If some kind of vibrating household device, which operates on the tuake -and- break principle frc>ta the house current, is in use, it will generate strong waves, which will probably be picked up by the receiver through its antenna even when "13" batteries are used. However, when the receiver's plate supply is obtained front the same power source as that operating the inter- fering device, the interference will be greatly magnified. In neighborhoods supplied with direct current for lighting, because of the fact that connections are direct rather than through Iron.sfornu,., interference of this For convenience fake character may attain astonishing volume. For this reason, additional importance is to be attached to the increasing vogue of constructing the power unit and amplifier -- General Electric' as at separate instrument from the receiver proper -It.F. and detector. Not only is Battery Charges' there greater flexibility in the use of a phonograph combination with the amplifier; but a small, highly- sensitive short -wave re- It's easy to keep radio batteries always at top ceiver may be used with the amplifier for notch power with a Tungar -General Elec- New low prices the purpose of receiving the programs now tric Battery Charger. Tungar gives a trickle Fart oftheRockies available from great distances. Even with charge or full rate to "A" batteries. And it a stage of R.F. ahead of the regenerative charges "B" or auto storage batteries, too. A 2 -AMP. $ 14 detector, as in the short -wave broadcast re- complete battery charging service from one TUNGA P. ceiver described in this issue of It.vno Nmvs, Tungar! the amount of current consumed by the two 5 -AMP. topes required would be but a small drain Permanently connected to a radio battery, T UNGAR on batteries and entail little trouble. charging is merely a matter of turning on $24 Tungar when needed. TRICKLE 10 Weighing in Radio Stations TUNGAR (Continued from. ¡nape 11'ág) For convenience sake let your radio dealer show you Tungars. There are three types receiver and a cone -type loud speaker. On serves a special purpose. He'll see of -each Guaranteed, the other end of the table were a pair that you get the right one for your particular scales and a number of weights, which were by labeled with the call letters of the popular needs. General Electric nearby broadcast stations. "Now, gentlemen:" continued Randall after the table had Moen mitred to the center of the room, "if you will suggest the call Merchandise Department Tunear -a registered letters of a station you would like to hear, General Electric Company trademark -is found Bridgeport. Connecticut only on the genuine. I will endeavor to show how my set oper- REG. U.S Look for it on the ates." Someone: called out " \1'.17." and IBATTERY CHARGER name plate. Randall selected n weight, pineed it on the scales and turned on the filament switch. Much to the surprise of everyone, the sig- nals from \CJ' /, were heard coming from the speaker. ,Tack ELECTRIC I)allaas was the most skeptical men- GENERAL

The BURT Cell he ,at h usa- cl l irtmtopouat fatigue. uIten lBelpn uce1- b le, aleanrieo In eAbd oROE: Stabilized Oscilloscope c, pjNM E ,s'125 The only visual osellloatraph having a linear time axis. ND (AVM an :it-curate picture of high frequency wave fono& S Write for Bulletin 273. DR. ROBERT C. BURT, 327 South Michigan Avenue, Pasadena, California. `rr>rgs Me Studio %íoNe SANGAMO AUDIO APPARATUS Balkite Fixed Condensers SANGAMO ELECTRIC COMPANY ItadioPower Units SPRINGFIELD, ILL Fansteel Products Co., Inc ., Nor th Chicago, Ill SHOT '`CORK to News a year. By adding shot to a hollow Insure your copy reaching you each month. Subscribe Radio -$2.50 weight and Y. C. plugging it with a cork, the tension can be Experimenter Publishing Co., 230 Fifth Avenue, N. determined at whirl, stations are tuned in.

www.americanradiohistory.com 1160 Radio News for April, 1928

ber of the party, and he immediately said "Sure, I'll be glad to," Randall replied: i!lifi`...... _.,.._. ._:_... :: that he considered the demonstration a fake. "This arrangement is the easiest thing in To prove his point he placed the WEAF the world to fix up, but it takes considerable weight on the scale and to his surprise time to make weights of the correct size. WJZ's signal disappeared, but WEAF was The first thing you need is a loop -operated not heard. Randall immediately explained radio receiver, which may be tuned with a that he should remove the WJZ weight, and single variable condenser. In most cases then WE/a' could be heard. This was the set must have three stages of untuned tried and found to be true. All persons radio -frequency amplification, as .other sys- 'in the room then became interested and, for tems usually require a more complicated tun- the next hour, we tried placing the various ing arrangement. The size of the spring weights on the scales; and, in each case, coil isn't very important; as the set can be the loud speaker brought in the signal of adjusted to the desired waveband with the the station which was called for. variable condenser and then the weights may be used to select the various stations. on THE SECRET EXPOSED! Twenty -five turns of aerial wire wound a hat box are used, and they make a very When Randall was asked for an explana- satisfactory loop antenna." tion of his new receiver, he lifted the table "There are any number of systems which cover and disclosed a large coil spring which may be followed in making the weights, and had been concealed beneath the table. none is very difficult. I used some weights qe -Day only "It is very simple," he explained. "The which I found in the laboratory and filled Guarantee O coil spring which you see under this table them with a sufficient quantity of shot to An absolutely unequaled acts as a loop aerial for the set on the value! We want you to test LOW; tune in the desired station. However, pill the World "A" Socket Power Balance table and, at the same time, it serves as the boxes, which you can buy at any drug store, Unit and compare it with . any other of two or three C.O.D.J grid coil for the first R.F. amplifier tube would be just as satisfactory and might times the price. Try for ten the You will notice that one 'end of our risk. Then of set. make the trick even more mysterious; as hat it tis unsurpassed as f too quality and wonder- the coil is attached to one side of the scales they are all of the same size. It is also ful results. purchase price will be refunded in lull. Operates on 50 or 60 cycles at 110 volts in such a way that, when weights are placed possible to add to the trick by placing a A. C. Highest quality Westinghouse electrical equipment. No hum or noise. Approved by Radio on the other side of the scales, they will weight in both pans of the scales. Oi course, News Laboratories and other leading Authorities. cause the coil to expand in length. Prob- the weight in one of the pans wouln be the Send Order Today yoérnameJust write and ably you know that the inductance of a coil same for all stations, and the weight in address on a slip of paper pin a dollar bill between to it and mail today. We ill ship same day decreases as the separation the the other pan must be changed each tine" order is received for $12.75 C. O. D. 5% discount turns is increased; and this principle is "Now that we know what it is, and how for cash with order. Remember you are the judge and are fully protected -so send order used in tuning the set. A heavy weight it works, tell us how you thought of the NOW. placed in the scales will greatly increase the idea, and why," someone asked. length of the coil and, as a result, tune the "Well, I'll tell you," Randall answered: Vta-0)4WW/Ir,444 set to a low wavelength; whereas a much week, 1219 South Wabash A "Last while experimenting with my Dept. 60 Chieago, 111inois lighter weight is used for the high -wave new invention, I dropped niy fountain pen by f Station operated )p, station." and its weight on some wires changed the World Batteerryn Comps "Well, Randall," exclaimed Jack Dallas, inductance of the circuit enough to tune in "Your set provides a fine after -dinner trick, a new station. That gave me the idea and even if it isn't of much value to the radio I could not resist the temptation to have industry. Give me the full details sometime some pleasure at the expense of a few curi- so I can fix up a set to fool the folks back ous persons who have tried to find out what home." I am doing in the Lab."

When the SOS Flashes

(Continued from page 1109) AT YOURJERVICE THE HOTEL WHITEHALL January 7, 1904, establishing "CQD" as the 14, 1912. As soon as the plight of the big ICO " ST. AND BROADWAY NEW YORK official distress signal on and after February ship was realized, Captain E. J. Smith or- 1, 1904. dered Operator Jack Philips to broadcast 7THE ideal hotel selection when At the Radio Telegraphic Conference in the distress call. Immediately the aerial of you visit New York. All rooms shower and at Berlin, in 1906, the German government the sinking vessel radiated "Come at once! have both bath and suggested rates of $5 per day for two! A per- "SOS" to replace "CQD." Ger- We've struck a berg! It's a CQD, Oit!" fect hotel. Ample parking space man ships had previously used a call "SOE" (The "OM" is the radio sign meaning "Old aqd near numerous garages. when they desired to communicate with all Man," which adds a friendly personal touch exceptional Restaurant other vessels within range. Since the letter to the dots and dashes.) "E" consists of only one dot it is easily sus- J. J. McAULIFFE -Res. Manager Then Junior Operator Harold Bride sug- ceptible to loss by interference; so the dele- gested, "Send 'SOS.' It's a new signal and allaCiatagataggiallalliaaalaaelki gates suggested that "S" be used as the last it may be your last chance to send it." So letter. "CQD" was superseded in July, 1908, Philips flashed "CQD" and then "SOS." by "SOS," selected as the international dis- "CQD, 'SOS' from MGY. We hare struck tress call by the Radio Telegraphic Conven- iceberg. Sinking fast. Conte to our assist- tion held at Berlin. (To be exact, this call ance. Position Lat. 41.45 N., Long. 50.14 W. differs from "SOS" by the fact that the May." (MGY was the radio call of the Build LACAULT'S Latest groups of dots and dashes are not separated Titanic.) ALL WAVE ELECTRIC like separate letters. This gives it a strik- Philips went down with the ship, but Quirk ALL PARTS Shipment IN STOCK ing and attention -compelling note.) Bride was among those rescued by the Car - "R. EA.. 9" The acts of the convention were not rati- pathia. That tragic scene enacted in mid- Write for our list of "Specials" fied by all nations until about a year later, eta-an proved without a doubt the true value -lowest prices in country. so "CQD" remained in force long enough to of "SOS," the call that still vibrates the call rescue ships to the wreck of the Re- ether as a signal for help and silence. . ACFI ULT a' public in 1909. And so loud speakers become quiet when 10 LECTjüC ABORAjOR/ES "SOS" came into prominence when the it sounds, as if to pay tribute to those who 116 WEST 65th STREET NEW YORK CITY Titanic sank in the North Atlantic, April have. "gone down to the sea in ships."

www.americanradiohistory.com Radio News for April, 1928 1161 How Powerful a Tube Does Your Set Need? (Continued from page 1137) point is reached where, on loud signals, ø'i'Groud serious distortion occurs, owing to the fact that tubes of this type have a comparatively high amplification factor, so that signals of even moderate intensity drive the grid posi- tive. This overloading, in the case of the 201A type, occurs long before the volume has reached a point commensurate with the requirements of the listener, and before teria Gets Everything but Static! sufficient current is flowing in the plate cir- cuit to reproduce accurately the bass notes. Brings in Far Away Stations In a broadcast station, for example, only Loud and Clear Regardless of signals of little more than telephone inten- sity are expected from tubes of the 201A Static Conditions type; whereas, in the set of the average Bans everywhere are replacing their troublesome and static gathering up-in- the -air aerials with the radio enthusiast, they are expected to fur- marvelous new GROUND ANTENNA- Aer-O- Liminator. Radio engineers and hundreds of users nish unlimited volume. testify that Aer-O- Llminator gets better long dis- tance reception, almost unbelievable freedom from outside noises, far greater selectivity and marvel- ously true. clear sweet tone Quality. John E. Christenson, Radio Engineer, Chicago, When Radio Turns Street writes: I have tested and thoroughly approve the Aer -O- Llminator. I lind it Increases selectivity Lamplighter and volume without distortion. ornetitally elimin- ates static, gives good clear tones. both on local and distant stations. 1 would recommend the use of (C'onti.aed from page 11.20) the Aer -O- Llminator to every radio owner to get the best reception from his set." months. The receiving circuit is extremely simple and requires no tuning or adjust- FREE TRIAL ment. In other words, it is an automatic Make this thrilling test at our risk! receiver and the I)X faun would scoff at the Install an Aer-O- Llminator (Ground Antenna). service of such an outfit, operating at only Leave your old overhead aerial up. Try out on a night when static Is bad. If you do not get a One frequency or wavelength -40 kilocycles wonderful improvement in freedom from static. greater selectivity and clear sweet tone without or 7,500 Meters- which is outside the broad- interfering noises, it you can't get good reception on stations tha are drowned out by static on your cast band. old aerial, you need not tray as a red cent for this the first commercial test. Send coupon at once for scientific explana- This :narks applica- tion of Aer -O- Llminator (Ground Antenna) proof EASY TO INSTALL hole ab out tion of radio as street lamplighter, but a of performance and our Conclusive iron-bound .1usu. dig a small remarkable Free Trial Offer-Mall (i inches in an.1 su newhat similar radio service is operating Coupon TODAY! drop er - O -t lrih er into it. in Washington, 1). C., where the electric- power distributing company has installed two small broadcast stations and equipped its repair trucks with radio receivers, for .Aer-O-I.4iminatbr the purpose of maintaining communication between headquarters and the repair forces (Ground Antenna) afield. These, and developments of a like vein, suggest the daily unfoldings of radio in strange fields and likewise explain the Endorsed rush by various industries for government f by CURTAN licenses to use short waves. Erie 1 Chicago . Dept Foremost 827-E. 1 ( aePlease at Stlcn semime once complete Engineers 1 Lf ; with dese i,11 .end FREEdetails paon of OUR TRIAL OFFER. tutee, and 1 Name.... APRIINL ISSUE: 1 .. The Story of the Days to Come, Dealers I by H. G. Wells. We are always City.. t interested when we read a story ...... Stute...... of the far future, and of the .. 1 wonders that might be in store for our descendants. But when I...... t such a story is written by Wells. it he- CURTAN MFG. CO. comes all the more realistic and the more 154 East Erie Street absorbing. Dept. 827 -E Chicago, Ill. The Miracle of the Lily, by Clare Winger Ilarri s. Insects are and were man's DEPENDABLE BATTERY POWER greatest What WHOLESALE "B" enemy. if they should gain AAOIO CATALOGUE ascendancy over human brings erice nuore? The author, who was the third prize ' 77e Boa( theq winner of our $500.00 contest, weaves a are altalkorgabout fascinating story around this idea.

The Return of the Martians, by Cecil 13. White. Being an astronomer, our author is well informed on the subject and in this WHOLESALE sequel to "The Retreat of Mars," he gives us a most unusual, as well as powerfully RADIO CATALOG written, story, which is not too technical. Listing thousands of Items in standard radio parts, Kits, Accessories. Complete Sets, Fur- Baron Münchhausen's Scientific Adven- niture, etc. Every Set Builder and dealer tures, by Hugo Gernsback. Our resourceful should have a copy. Real wholesale prices. Send Baron. in his quest for further first -hand for your copy today. information 100 Volt Edison Element. about the universe, lands on THE on Destructive, Rechargeable "II' Battey mat \tars. HARCO COMPANY charger. Shipped dry with solution, s o. 140 Volt with 1257 So. Wabash Ave. Chicago, 111. charger. S17. Free sample cell. See ane It :monies. The Ancient Horror, by lial Grant. Pre- Sf1Nf) NO MONT-X -PAY EX 'itEssltIAN historic monsters are no novelty in Write for our Free Illustrated 28 -page Booklet litera- 'The H A RC O CO. /159fo7Uaáashvc.Ctiicag SEEJAY BATTERY CO., 915 Brook Ave., New York ture, but here is one so totally different you will not be at all sure that it is not entirely truth.

And Others. Insure your copy reaching you each month. Subscribe to Science and Invention -$2.50 a year. Experimenter Publishing Co.. 230 Fifth Avenue, N. Y. C.

www.americanradiohistory.com Radio News for April, 1928 How to Pick An Audio Amplifier (Continued front page 1142)

circuit shown in Fig. 3 illustrates the way tube from passing through the windings of 1c--)`nT( PlU> in which it is accomplished. the loud speaker. AJti')72 W;-..) It is not within the scope of this article MAfitun' !60, USE OF AN AUTOFORMER to discuss the problems of transformer nut .t ok O EXPERTS design, but it may be said that the quality Fig. 3 shows one stage of an impedance - of reproduction obtained from a trans- capacity- in which - C".) coupled amplifier an auto former- coupled audio-frequency amplifier is former is used in place of the usual audio largely dependent upon the electrical char. choke coil in the plate circuit. The auto - acteristics of the audio transformers which former is identical with the usual audio are used. Of course, the selection of the choke coil, except that it is wound with proper tubes and the use of the correct more turns of wire and a separate tap has grid and plate voltages is ,just as important been provided for connection to the plate in this amplifier as in any other amplifying of the tube. As the circuit is arranged, the apparatus, but it is equally necessary to entire winding of the autoformer is con- have correctly-designed transformers. nected in the grid circuit of the tube; but only a part of the winding is in the plate PROPER circuit. This arrangement produces a volt- TURN RATIOS Radio Fans! age step -up in much the saine way as does In the transformer- coupled amplifier the a transformer, the increase in voltage being amplification per stage is equal to the am- plification constant of the tube multiplied get together by the ratio between the turns of the sec- ondary and those of the primary windings Of the transformer. Thus, if a 201A tube with LP RG is used in the first stage and the coupling r transformer has a turn radio of 3:1, the TAP.- amplification of the stage will he equal to RADIO 3 multiplied by 8 or 24. Several years ago, when the public learned NEWS VV the fact stated above, it gained the impres- sion that, in order to increase the volume of a set, it would be only necessary- to em- Amateurs' ploy a transformer with a higher turn ra- Handibook tio; and the poor results which were ob- j tained with high -ratio transformers were lui'rel- responsible for the "black eye" which and get the 8+ A- B- A+ transformer- coupled amplifiers received at FIG. 3 the time resistance- capacity coupled ampli- big things done! fiers were first introduced to the radio set - building fraternity. HEREHERE is a brand -new edition of the When autotransformcrs are used in place of It has already been explained that trans- impedance units in an impedance-capacity- articles that have ap- coupled amplifier, the above circuit arrange- former design is too large a subject to cover peared in Radio News, Radio's Great- ment is employed. in this article; but it must be pointed out est Magazine. that the turn ratio of a transformer does not determine its quality. 'l'he fact is that, big the higher the ratio of a These are the things -the determined by the ratio of the number of turn transformer, the more difficult it is to build a which high lights in Radio achievement! hums in the entire winding to the number unit will give good reproduction. Usually it with of turns in the plate section of the winding. Plenty of the latest circuits, will be found that transformers with a high diagrams, construction details, and all In a circuit of this type the amplification as high as one and one turn ratio have insufficient turns on tit necessary data for the set builder. per stage is often winding half times the amplification factor of the primary and have a large capacity effect between All the latest -most far advanced tube. the primary and secondary windings, with the result the the Radio World that instru- methods known to - ment gives very poor efficiency on both the amplification, shielding, parts -every- TRANSFORMER COUPLING high and the low tones and in the middle thing! Fig. 4 presents the schematic wiring dia- range the amplification is full of resonance This is the greatest Radio Handibook gram -of a standard two -stage transformer- peaks which distort the music. Voice and music from such an instrument is often ever published. Size 9 x 12 inches -116 coupled, audio- frequency amplifier. This is type of audio distorted to point where it bears but slight pages -fully illustrated -elaborate dr- probably the most popular amplifier in use today, and the reasons for resemblance to the original. diagrams- -everything convenient cuit its popularity are not difficult to understand. On the other hand, the reader should not for the fan. It provides a wcry simple method for se- gain the opinion that all low -ratio trans- curing maximum amplification from a given formers give good quality, for such is not number of stages. It is more foolproof the case. There are ninny good transform- than either of the other two systems de- ers of the low -ratio type, and there are 50c. scribed, and provides ample volume with ninny- which do not give ideal reproduction. two tubes. However, it will introduce dis- For an example; we will say that one manu- ON ALL NEWSSTANDS tortion if equipment of the highest quality facturer makes two different types of 3:1 is not selected. ratio transformers. Both transformers are wiring diagram it may be seen size, If your newsdealer has none on From the the same shape and approximate that the tubes of the amplifier are induc- weight; but one delivers only average quúl- hand, write direct tively coupled together by means of a trans- ity and sells for about $3, while the other former, the primary of which is connected delivers practically perfect quality and sells EXPERIMENTER PUB. CO., INC. in the plate circuit of one stage and the for $10. In the case of these two trans- secondary in the grid circuit of the follow- formers the color of the case is the onl- York 230 Fifth Ave. New City ing one. In the drawing T1 and '1'2 are way- in which they may he distinguished by the two interstage coupling transformers; external examination; so it may be seen and T3 is a 1:1 -radio output transformer that the person who desires liest results which prevents the plate current of the Last mint buy quality equipment and cannot

www.americanradiohistory.com Radio News for April, 1928 judge the efficiency of a transformer him- self. It must also be explained that the range of frequencies over which uniform amplifi- cation is obtained in a transformer- coupled amplifier is never as great as in a resistance - capacity- coupled- amplifier. However, this is not always an undesirable characteristic. A modern broadcast station transmits fre- quencies only within the hand of 30 to 5,000 cycles; and there is no reason why the audio amplifier of a radio receiver should reproduce over a wider band. In fact, when an amplifier reproduces sounds having a fre- quency of 8,000 cycles, many circuit noises and hissing sounds are amplified; and these "I have used cause interference with the music. There- ACME PARVOLT fore, if a transformer which amplifies effi- Condensers for ciently over the range mentioned is selected, many rears and it is possible to have reproduction which hate never Izad at break down." closely approaches the original. Showing the well -known L. C. 23 wired for A. C. power Dspply. Only the fiocco parts are specified in this high

( (_.0 ii I in I((/ front page 1103) would be of benefit to people who live in places where newspapers arrive too late in the clay to inform then of the current pro- 6-Whether grams. You Buy or Build At the present stage of affairs, radio ex- perimenters cannot hope to build photo- a Power radio receiving apparatus of the kind de- Supply Unit for Your Radio scribed in this article. The Moore neon lamp, which is the heart of the equipment is absolutely necessary for its and which ! successful operation, is not available at PLAY SAFE WITH PARVOLTS all; and, according to such high officials of the Radio Corporation of :\nu rift as David Sarnoff and Dr. Alfred N. Goldsmith, WHENWHEN you buy an electrified radio Condensers rapidly replacing ordi- it will not be available for private use for power supply unit for your re- nary condensers in electrified radio. several years. Besides, special mechanical, ceiver, look for ACME PARVOLT Con- These condensers are wound with optical and photographic apparatus, such as densers; they are your guide to quality the very finest insulating papers, only a very fully -equipped physics labora- in all other parts. They cost the combined with highest grade foils. tory would possess, is essential for the con- manufacturer a trifle more, but they Every detail produced in one of struction of the picture receiver. are both his and your guarantee against America's most modern plants ILvno News, therefore, requests its read- costly condenser break -down. and in details of under the supervision of ers not to write for further power the system described in this .article. No Should you build your own experts in condenser design and constructional information of any kind can supply, be sure to use ACME PARVOLT manufacture. be obtained from the designers of the ap- Condensers and be safeguarded against Uniformity of capacity and uni- paratus, and even if it were available, it the possibility of break formity of sizes are would be of little practical value. When down. Remember that two big features. Ac- television and radio photography develop poor filter condensers curacy of all ratings, out of the laboratory and single-demonstra- caused untold thousands based upon the R.M.A. tion stage, and when regular experimental of dollars worth of loss is then RADIO standards, another transmissions are inaugurated, in the past year or two, NEws will supply its readers with practical guarantee of uninter- data which will enable them to construct for blown out conden- rupted service. Play working machines. Until such a time, the sers mean blown tubes, safe with PARVOLTS! editors will discourage the publication Of burned out transformers Made by THE ACME half -baked information dealing with so- and frequently the ruin- WiRE COMPANY, New n-tiled television and photo-radio equipment ACME PARVOLT FILTER CONDENSERS ation of speaker units. In all required mfd. capacities for zoo, Haven, Conn., manu- never existed outside of the designer's 400, Soo, solo, ',Alai Just as PARVOLT By- 600, and tgoo Volt D C facturers of magnet and imagination, and the materials for which requirements.f Supplied singly or In am- Pass Condensers have p er wired ¿loth the important enameled wire, var- can he procured only by someone possessing power been used for years it supply unit,. nished insulations, coil a skeleton key to the General Electric ACME PAR VOLT BV -PASS CONDENSERS laboratories. high -grade receivers, so Supplied in all required mfd. capasitie, windings, insulated tub_ are PARVOLT Filter and for all standard working voltage,. ing and radio cables.

A VOLUME CONTROL Loud speakers, gramophones and dogs are forbidden in some West Surrey flats. We understand, however, that the tenants are al- ACME PARVOLT CONDENSERS lowed to play cards, on the condition that Made by the Marfufacturers- of the game is whist. --London "Humorist." ACME CELATSITE WIRE ENAMELED CELATSITE ACME MODERN MOTHER GOOSE AERIAL WIRE REn I-Ioon: "What big ears you FLEXIBLE and SOLID SPAGHETTI Rmiso . }e Enameled copper in loth stranded and For all types of radio :Tiring. Binh A superioi eambrir tubing for all have, grandmother!" solid types..41so Acme Lead -ins. Battery insulation raine; non- indaninaable. practical radio and other electrical GaAxI »rop11Ex: "All the better to listen - Cables, Indoor and Loop Aerial Wire. lo colors. requirements. Supplied in IO colors. in witli, my dear. " - Popular Wireless, Lon- don.

www.americanradiohistory.com 1164 Radio -ATugs for April, 1928 The Old Dray Mare

(Crhilted front page 1111)

the rush act. They tries to pocket her, but credit, he holds his audience -"is n sec- don't succeed; again I wins, this time $230. ondary coil, part of an alternating- current Little Joe is very happy. inductance. It is half of an ingeniously - FREE! I don't even see The Master all morn- contrived step -up transformer. 6 TUBES ing, though I mingles with the gang at the "Shortly after the first race, when I had UX 201 -A TYPE .n fair exhibits, and eats hot dogs until I'm by test established the method that was be- (Tested and be wired 'Watched - in a few minutes barking. ing employed, I searched the old stable noon it to cloud up, and for An amazing value timt can't be beat! Lat- At starts across from the turn. Concealed therein, est six -tube tuned radio frequency circuit. about half an hour it rains. Not hard, but dis- Extremely selective, marvelous sensitivity. and plugged into the lighting circuit, I Three stages of radio frequency, detector, enough to muddy things up considerable. covered the primary that actuates the sec- and two stages of low ratio audio frequency for improved tone quality. Two -dial control. Strafght- I tries to locate Jerry, but he's disappeared. ondary here in the saddle. There was other line frequency condensers. All metal chassis. Shielded. Clear and realistic reception guaranteed. Beautiful black The rain stops before race time, and the apparatus deftly connected with it, in such front panel7 in. a 18 in.) ; ornamental design, de- comes slow, and I kilocycle markings gold. and sun out, but the track's a manner and so wired that when the cur- sub -panel rote sis. No ra parts to buy. l ain't got any dope on how Fuse Plug acts rent was on, and the horse passed the barn, Parts mounted. SimPlySimply connect a few wires. No special tools needed. Kurz- lCasch indicator knobs. New type in mud. Finally, I decides to slip my morn- she received directly through her spine a I'X sockets. All hook -up wire and colored battery cable included. Value 860.00; our price, $18.86. ing's winnings on the snare, and take a very strong shock -I have not yet deter- TESTED AND APPROVED the favorite and the Severe laboratory tests have proved the remarkable chance, although she's mined the exact potential. But it was suf- efficiency of this set. Owners everywhere are sendinu us best I can get is even money. I'm figuring ficient to spur the mare on and, as the letters praising its wonderful receptive qualities. "Wired in short order. Getting stations all over the co un- strong on the external impulse. pressure lessened with distance, common tsetrv. Plenty of volume. The set sure is a dandy." B. J. Gillis. Denver, Colo. Telegram from M. A., Syracuse, There's only seven in this race, and none sensemlust have kept Fuse Plug running N. Y.: "Ship at once two mere Stuperphonics." SIMPLE WIRING DIRECTIONS of them seems to be a mudhen. They starts, until the distance eliminated the induction." Very easy to wire this set with the instructions we fur- with Fuse Plug bringing up the tail end, no nish. Just connect a few wires. All you have to do Is There's a round of applause, but the to follow numbers. That is all. Can be better nor any worse. They're slowed, but wired in a few minutes by anyone. No mayor's still there with a question. radio knowledge needed. Make money as a whole; up and around the bend they by w-iring these sets in your spare time "You said radio," lie reminds. and selling them to your friends. splashes, the mare trailing, until they comes abreast of the lab truck. Jerry smiles faintly. "Indeed I did. You Then the nag gives the expected lunge - see, when I first heard of Fuse Plug I sur- .list write your name and address on a post card and and how! Fuse Plug takes half a dozen mised to an extent the method that was be- ask us to send yon this great outfit with six tubes. We ship right sway. t'pon arrival pay only $18.95. plus a frantic leaps, forges to the front, her mouth ing used. On her first race Tuesday I veri- :small delivery charge. (Foreign countriessend $19.50 with order. We pay shipping chore's.) frothing. Twenty feet from the tape, four fied my hunch. This morning, before the Radio Equipment Co., Dep.12 -D 549 S.Wells St., Chicago lengths ahead of the rest, Fuse Plug stops, first race, I discovered the apparatus in the flops, and slops-in requiem, so to speak. barn. I didn't have time to open a box Changes Your Set Hint contained some of the device, be- as the part Into a Short -Wave The grandstand rises en masse cause I had to get back to my truck to get Plug lias Receiver field thunders past, but Fuse been set for the first race. blown out. Sent postpaid anywhere in "I saw nobody enter the barn, and all en- U. S. upon receipt of 515.00 They carts her remains to the stables, M. O.. or C. O. D. plus trances were visible from where I was Postage. upon receipt of but before they can do anything The Master 51.00 to guarantee carrying parked; when the primary functioned, and charges. his detective an em- exhibits badge -he's with no one tó operate it, I was puzzled, but When ordering state kind ployee, valued, of a well -known of sot so that detailed di- and inter- only for a moment. rections for use may be national agency -and makes for the corpse. given if necessary. Also after the first race this state type of tubes. such as 'l'he owner and trainers make futile efforts "Immediately UX199, ÚV199, W011, or morning I returned to the barn. No one 201A. to hold him back, but with the aid of the local sheriff he gets there. was there. But this time I took apart the The SUBMARINER box that I previously had not had time to ex- Regardless of the kind of set you bave, this device will permit Quickly he removes the saddle and look into. This box contained a radio re- you to listen to short -wave stations between 26 and 68 meters. amines it. Operates with sets such as T. R. F., Neutrodyne. Super- Hetero- ceiver, tuned to one wavelength, and operat- dyne, regenerative sets. and many other types. No additional tubes or batteries required. No changes to the wiring of the "As I thought!" he exclaims, triumphant ing the main switch to the primary! set. A short aerial and ground Is connected to the "Sub- shown two small contacts, mariner." and a cable and plug attaches It to the set. We're copper "The actual control was indeed remote. Requires less than a minute to attach or detach. Operates about three inches apart, on that portion as a wave changer with Super-Heterodynes, and as a detector It took me an hour to find the wavelength Unit with others. of the saddle that is directly over the horse's the receiver was set for; I returned to my SHORT -WAVE RECEPTION backbone. truck, arranged my own receiver as near Is practical because they penetrate better. and there Is lass There's a noise in the crowd, and a big, likewise as possible, set up a loop for di- static. There are several powerful stations using the wave band covered by the "Submariner" for broadcasting programs. You portly guy breaks through.. He eyes us rection- finding, and waited. may also learn code by listening to amateurs from all palls of the world. You will have a highly efficient short -wave receiver when sternly. "What's this ?" he demands. "On the last race I had but a few seconds the "Submariner" is attached to your set. Nothing else like it on the market. Take a trip in the low waves on board the Jerry shows his badge. "I have been en- to tune and get may directions in, and it 'Submariner." deavoring to ascertain the secret of this had to be done against the interference of ORDER TODAY horse's former spurts of speed," he ex- the operating primary. But I located the ire guarantee to refund if Ike "Submariner" fulls ro operate ADDRESS plains. "I have found out" transmitting station -in the Belvedere Hotel J -M -P MANUFACTURING CO. He shows the fat man -who happens to across the street!" Dept. 120 Milwaukee. W s. be the mayor -the saddle. The official No sooner said than a deputy comes up grunts. "Battery, ch ?" with a small, scraggly guy handcuffed and MAKE RADIO PAY YOU The Master shakes his head. "To the surly. It develops, after questioning, that contrary, no. Strange as it may seem, Fuse he is the genius behind the fracas. -HE DOES! Plug was controlled by radio !" Until then it hasn't dawned on me that This man is a "Y" This statement gets a stir outa the I've lost all that I made. I turns to The graduate.. As a Master, forgetting our agreement. radio operator, he crowd, but nobody gives him the bird. The has interesting, mayor squints at Jerry, and spits out a wad "Say, Jerry, how come the nag passed well paid and of tobacco. out ?" 3 know, too. pleasant work. "Radio ?" he queries. "Whadda ya mean, There's others that want to You, too, can suc- Master smiles, and then gazes sadly at radio ?" The ceed in radio. Our the remains of the horse. Jerry loves ani- courses quickly qualify you. Write "Just that," replies The Master. He rips mals. today for free booklet on open the saddle, displaying a network of "In planning their radio control, the con- "OPPORTUNITIES IN RADIO." fine insulated wire, the two ends of which spirators were very clever in making plans terminate each at one of the copper con- West Side Y.M.C.A. Radio Institute for their personal safety," he states. "But tacts. they thought their scheme so se- 319 West 57th Street, New York, N. Y. evidently "This," explains Jerry -and, give him cure from detection that they didn't even

www.americanradiohistory.com Radio News for April, 1928 1165 bother to visit the barn to look at the ap- paratus before each race." "Didn't dare," mutters the radio operator. "Looked suspicious." Serksational The Master nods. "As I surmised. But the rain leaked in on the wiring, and caused a `short' when the switch was thrown in. Since water increases the natural conduc- Success tivity of ea rib, and the ground at that end Of Tile track was almost a small pond, poor Tested -- Proved -- Read These! Fuse Plug got it cooling and going. It was "The Eliminator buughr from you some time ago is every bit what you a bit too much for her old carcass. She Over 35,000 Times claim it to be. Get greater dblrnre, volume and selectivity than I ever tried to get away from it by crossing the did with "R" batteries. We defy anyone, anywhere, to match the quality and per- Charles Hoather, Kingsville, Ont. tape, as experience had taught her she formance of the Townsend "B" Socket Power -performance "The Eliminator numb:lard from you could. But this time the mare couldn't that it is your privilege to obtain for only 86.85. Thousands some time ago Is very satisfactory of reporta show astounding results beyond the capabilities of and in constant use." quite make it." many of the highest- priced "B" Eliminators. Convince A. T. Alexander. Canty, Ore. yourself without delay at our risk. "The Eliminator received last June shakes and asks us to is still working fine on our D. C'. 'l'he mayor hands, current." Sgt. J. Meliinncy, stay for the big dance in the evening, but Alcatraz, t'alit. "The Eliminator I lutughl from you The Master hates being stared at, so we A.C.-D.C.--Any Cycle about a year ago has given Rant arr- vice. No hum or any of noise you Island, use minus my Delivers up to 100 volts on any set. Full tone, clarity, the breezes back to Long and volume. Sold on OF get from run -down bat (erica." REAL GUARANTEE MONEY A. L. Babermehl. E. St. Louis. Iii. long green. BACK IF NOT SATISFIED. "Your Eliminator is certainly work- ing fine. I get better recent ern than "Why didn't you tip me off ?" I ditmands. I lave had since I owned the set:' too Ed. Beaudry, I,ub'ul:e. MI., "After all your good advice on the sub- 'I have much pleasure In telling viii SEND ONLY $1 that I have had complete sat i fart luu ject, I never thought you'd bet on a horse," with the Eliminator purrhasd from declares Jerry. "I low munch did you'lose ?" Simply fill out the coupon and slip it into an envelope with Xyou last May.' only $1.00, and mail at once. Your Townsend "B" Socket D. H.t\'.Taylor,Verdun, Quebec../ I grunts. "Oh, I'm even -just lost what Power Unit will be sent promptly. Deposit only 85.85 plus postage with the postman. out for IO days a Try -then iaude. But like fool I got generous last if it does not do everything we say, return it to us and night and promised Doris a new set of fur- purchase price will be refunded. niture for the parlor." TOWNSEND LABORATORIES "What kind does she want'?" asks Jerry, 713 Townsend Street Dept. 25 Chicago, Ill "Mohair?" MONEY BACK GUARANTEE "No," I growls, "horsehair!" (Copyright, 1928, by Robert Francis Smith) Townsend "B" The Radio School Teacher Socket Is Here Power (Continued from page 1117) Approved and passed by the lh' expression Of all nil activities. These rigid laboratory attitudes were reflected in the conduct of tests of Popular the children on the way house from school, Radio a n d Radio in their homes and in their communities. News Dana S. Merriman, musical director of 11-TIC, and other members of the station daft' are enthusiastic over the success of the course. Atu o'n Only Anyone who followed a group of pupils $1.0 Couponothia t'roum their school to a home, where they were - - invited to listen to the radio music lesson, TOWNSEND LABORATORIES would have noticed that the well -bred ones 713 Townsend St., Dept. 25 Chicago, Ill. rhowed their good manners and that the Gentlemen: Attached find $1.00. Kindly send at once Townsend "B" Socket Power underprivileged quickly imitated them. They Unit, C.O.D. for $5.85, plus postage, on dll removed their rubbers outside the (boor. guaranteed 10.day free trial. 'Pile buys courteously waited for the girls Name to enter first. Each thanked the hostess for her hospitality as they left. I Address

Said for City State 1.11rrnbue I, CONNECTICUT SHARES ITER BLESSINGS a-r._ _,tee- - - Mow am I r MEP MI. .1. -1=11. Other states benefit from Connecticut's radio course. 'l'he eon muissioners of edu- cation in Massachusetts, New I-Iampshire HOTEL $7510 425Weeld and Vermont appointed music supervisors ChargingBatteries to net with the advisor:' committee appointed FORT SHELBY y$0' hy_ the Connecticut commissioner; schools Lafayette and First, You F : ¿Startsme show '% in Maine receive(( the lessons also. Private DETROIT Let you how 4 and parochial schools and many houses to make big money 22 stories; 900 rooms; beautifully right from the start. heard and appreciated then(. I've prepared a FREE every convenience. Radio undoubtedly will play a larger part furnished; book explaining all details. First Shopping, theatrical and financial week's profit pays for all equip- in our schools in the future. A large num- ment. You can get all the battery practically at the door. ber of schools have heard President Coo - districts charging business in your community with my Comfortable rooms at $2.50, $3, Service Station Charger-it's years ahead of or- lidge's addresses, by means of radio le- dinary chargers - handles 50% to 70% more ceivers loaned for the occasion. One state $4 a day; also higher-priced rooms batteries. I explain everything -start you in a and suites overlooking city, river, of your own and put you on the way to school official is musing radio as a means of business and Canadian shore. Servidor big money. Write for FREE BOOK. "visiting" his schools; he can reach more Engineer, Dept. throughout. Guests' cars delivered C. F. HOLMES. Chief R.N than a I bred at a time. The broadcast- Independent Electric Works Ill. ing companies are ready to cooperate with without special service charge. 5116 Ravenswood Ave. Chicago, the schools, especially because the schools J. E. FRAWLEY, Manager can be reached in the morning and early

www.americanradiohistory.com 1166 Radio News for April, 1928.

afternoon when the air is uncrowded and by excessive condensation. The out-of -doors many stations lack an audience. is calling. A vaudeville artist has to entertain his IF YOU WERE IN SCHOOL TODAY audience for about twelve minutes, and he faces a new audience every time he (loes his Think back to your own school days. act. A school teacher-and many are very Education has progressed, but still it fails young and inexperienced-must interest her unless it can secure attention and excite group five or six hours a day, five days a interest. There are 5,000,000 within our week, forty weeks a year, and there must borders who seem to be in the same fix be no deviation from the straight and nar- as the Florida cracker, who said that there row path that men higher up have laid out was only one thing that stood in the way for her. of his getting an education. That was "them Whether you were a teacher or a pupil, darned ABC's -there was so many of 'ein would you welcome a lesson by radio, with he couldn't learn 'em." music? The burden of education rests ultimately Would you like to hear Coolidge, McAdoo, on a teacher with a roomful of restless, AI. Smith, Will Rogers, Byrd, Amundsen, squirming boys and girls. They have to be Lindbergh? Would you? coaxed or forced through text books from The State of Connecticut has shown us which the breath of life has been crushed what to do about radio education. TIE ¡LIEVIISIION Wonder of A Nation -Wide Experiment in Radio Music for Schools the Age NE of the most ambitious experiments broadcast for the children, but to make ez- O with radio as an adjunct to its regu- plitnations more suited to listeners of more Complete Apparatus lar teaching facilities was made by the Matured minds. The lecture concerts will Not Costly New York public school system on Febru- be accompanied by sets of questions and ary 10 last when Walter Damrosch led the answers in order that instructors may, if Any Amateur Can New York Symphony Orchestra in a con- they choose, give examinations on the course. cert for school children. The program, last- "I should like to bring out most clearly Build One! ing one hour, was radiated over a network that what I plan is not designed to sup- of twenty -three stations, including WJZ, plant whatever musical training may already EVERY day TELEVISION and heard throughout the entire Eastern be in the course of instruction but rather is gathering momentum - half of the United States. to supplement the teachers' work. It is `the the shadow of its greatness is Mr. Damrosch's audience numbered at little red school house' in the rural districts already here. least 500,000 pupils in the seventh and that interests aie most of all, for these are Now is the time to develop eighth grades. New York City alone was districts where good music by a great or- with it -and as with Radio, be represented by 110 schools, whose com- chestra is so seldom heard." carried to the top of success! bined audiences totaled more than 100,000. Telegrams reporting reception of the con- SPECIAL INSTALLATIONS BE A PIONEER- cert were received from as far West as Many cities throughout the country in- BUILD YOUR OWN! Fairbury, Neb. stalled radio apparatus in the schools es- of the greatest electrical A message from the Listeners League pecially for this event. Among these were One said: "All the city 1)es Moines and Davenport, Iowa; Nash- companies has announced that it in Des Moines, Iowa, first schools listened to your programa. Children ville, Tenn.; Baltimore, Md.; Worcester, will be five years before the and teachers are enthusiastic." Fitchburg anti eighteen other cities or. commercial set can appear, but This telegram was typical of scores of towns in Massachusetts. Other telegrams this book, ALL ABOUT TELE- others that flooded in from the West, South reporting enthusiastic reception of the con- VISION, will show you how to and East and from the New England States. cert cauie from Georgia, where radio lws build a fine, workable set of In Worcester, Mass., the pupils of several been used in the city schools of Atlanta for your own -economically. And schools which were not equipped with re- more than two years. with it, you can take an active ceiving sets marched in a body to the City The enthusiasm outside of New York, part in the experiments that are Hall, where the program was reproduced for however, was no greater than that displayed in the 110 schools that which being conducted daily. their benefit. From Council Bluffs, Iowa, of city heard on four separate messages from the pupils of the concert. George H. Gartlan, director This is the latest book the schools requested Mr. Damrosch of music for the board of education, said: all is different subject-it contains that to continue the programs in the future. "The children who heard the concert were known. delighted, and we are already making plans PLANS FOR NEXT SEASON 116 pages -9 x 12 inches -fully for the broadcast next Friday. There is illustrated-diagrams-construc Immediately after the concert Mr. Dam - no question of its educational value. We tional details -parts rosch expressed himself as pleased with the are recommending to the board of estimate TELEVISION response which was pouring in by (mes- that all new school buildings be equipped ALL ABOUT senger, telegram and telephone. He spoke with radio. Equipping the old schools with optimistically of his plans for the coining adequate receiving sets is a matter that 50c year. will require some time because of the great on all newsstands "My plan for next Fall, if consummated," expense. he said, "is to conduct twelve concerts for If your dealer has none on hand "From time to time I have suggested to grammar school children, to be offered dur- local neighborhood organizations, chambers USE COUPON ing school hours and to be broadcast as of commerce and other civic organizations widely throughout the country as possible that it might he advisable for them to inter- EXPERIMENTER PUR. CO., 230 Fifth Ave., New York, N. Y. at that time. I hope we shall be able to est themselves in the movement to equip Gentlemen: I enclose 50c. for one copy of go as far West as the Rocky Mountains in with first TELEVISION. - schools their districts -class perhaps even to the Coast. receiving sets. Up to the present time NAME "Over a like period I hope to conduct these appeals have met with but little re- twelve concerts for students of high school sponse. The enthusiasm with which the ADDRESS and college age. The idea is not to pre- children received today's program should to interest among these CITY STATF sent music in these programs which will do much stimulate differ widely from that which was just bndies."

www.americanradiohistory.com Radio News for April, 1928 1167 Whispering Across the Hudson River 1 (Continued from paye 1123) And he The units operating the loud speaker are of the electro-

www.americanradiohistory.com 1106 Radio News for April, 1928 The Radio Beginner

(Continued front pi 112:i)

between filament and merely down" from the Send for Free Blue Print of the of voltage the grid current "stepped which may be compared to placing a charge house -lighting circuits, while others require NEW VICTOREEN on the grid. batteries or power units which contain A. C. CIRCUIT As 'explained before, the pick current is rectifiers. The "last word In Super Circuits -a continually changing in accordance with For detection, a small quantity of cer- Victoreen using the new A. C. Tubes. whatever variations in Here Is sensitivity. selectivity, and tone are present the tain gases, introduced into the glass bulb, quality such as you have never known original signal from the before. If you want to build the most broadcast station; often gives a tube greater sensitivity to remarkable receiver of the age, send for and, therefore, these electrical variations Free Blue Print, and complete con- small grid charges, "weaker signals." A structional details. are transformed into sound variations which tube to handle large amounts of power, and VICTOREEN may be beard in the telephones, and repro - such are necessary for good loud- speaker R. F.TRANSFORMERS duce the sounds originally converted into operation, must be of special construction Matched and electrical variations by the "microphone" so that the plate voltages necessary and tuned to a precision Of in the broadcast studio. A vacuum tube the power handled will not overload the one-third of used in this manner is called a "detector." tube; overloading:. daily give rise to tube 'f one per cent, y ì they are bBrge- failures. or distortion in the speech or music. 9 ly responsible No matter how rapid are the fluctuations for themntch- that are impressed on the grid, the plate less' perform- One of the governing factors in the use ance current faithfully follows these. Even such of 'a tube as a radio -frequency amplifier New A. [C. {.. Circuit-each extremely rapid variations as "radio fre- is the capacity between the elements of the tin $7.00 quencies," thousands of times more rapid tube. A special construction may, there- than the musical or speech ("audio") fre- fore, give better results for such purposes. VICTOREEN quencies, may be successfully amplified also. It is evident, therefore, that the design of "112" Audio Unit For further amplification, it would be neces- a tube is greatly influenced by the use which Combines two stages in the one case. sary only to connect the grid and filament Produces marvelous tone quality. is to be made of it; it may justly be said Price 522.00. of another tube in the position occupied by that there is a particular tube for each and New Victoreen Filament Transformer, the head telephones in case described in for use in the A. C. Set. Price 522.00. the every use in a radio receiver if best results New Victoreen Switch and Plug Unit- the previous paragraph, and the incoming are to be obtained. /or use In the A. C. Set. Price 56.75. audio- frequency pulsations could be still further amplified by the second tube. There CARE OF TUBES is no limit to the amplification that can be obtained, but various "extraneous" or out- The filament of a tube is designed to give side noises are also amplified; so that enor- best results at a definite voltage or cur- mous amplification may give too much im- rent, and at this value, a certain length portance to useless noises. of life for the filament is obtained. If the tube is operated at it filament voltage VARIOUS USES higher than the rated value, the electron Although the miction of all common radio evaporation is greatly increased, with little tubes is the same in principle, there are useful gain; but the life of the filament is other factors which determine which type very greatly reduced. Some filaments do of tube should be used for a given purpose. not actually. burn out when the voltages are Certain features of construction or the spac- exceeded, but they become "deactivated;" ing of elements may adapt a tube to some that is, the useful material has disappeared particular from the surface of the filament. This Enjoy use. Different materials and de- Louder, Clearer Signs in filament wires may be used; may often be restored by turning on the Better DX at our Risk so Why listen -in on weak. noisy. scnt- that different tubes require different bat- tube with somewhat above normal voltages chy, seauealy air waves whin ground tery voltages to operate them. fila- on the filament, and with the plate ("B") Wh, listen to fading. jumbled-up Certain distant reception when cnnÌ battery temporarily disconnected; but pre- earlike ments require more current than others for BUl AN t'ENNÁ-the eearnt and only is satisfactory device trpieku ground proper heating and "evaporation;" some vention much easier than a cure.

the sÌá eansa bmlae, tubes successfully operate from alternating The new "screen- grid" tube makis use of distant stati ons t itnvestyulletdisnever cd get d Approved by Thousands of Fans and Leading Engineers John White of Brooklyn. N. Y. plain- ly received both Melbourne and Syd- n L nia oNA tudbuact h -sixa e f 16.114 when an aerial bra uehtin nothing but Dodge. W. C. F. of Chicago gof Havana Cuba Rd Buenos Airee S.A. on a laborenna. Radio Newry Radio Age dm Digest and other trading labor, orie, approve and eecummen.1 Easily and quickly alled. Never needs :Monti.", {Pbaotenna.rim at once for wrticutarr of BREE TRIAL GUARANTEE OFFER which 'M yo to test SUHANTENNA on your act -'y at our rink. Weiitt"etodor emir CLOVERLEAF MFG. CO- 2711-C Canal St. Cbgaygo1.Iü. +.711II1111111IINn _.--.,. buée the Code Wireless or Morse-at home with the TELEPLEX Automatic Code Instructor. No better method for self instruction exists. Quick- Easy-Thorough. Endorsed by lU.S. Nat-a. The may Instru- ment that REPRODUCES actual sending -messages, radio- grams. etc. Any speed. Complete Course furnished. Thirty times as many words as any other instrument. Avail yourself of the TELEPLEX fora quick mastery of the code. Write for booklet NR- TELEPLEX CO., 76 Cortlandt St., New York, N. Y. SOLDEIZITE Insure your radio corny. ti,m by using SOLDERITE soldering fluid. ABSOLUTELY NON- CORROSIVE 2-ounce trial bottle 25c. postpaid. This type of circuit drawing explains snore clearly tete meaning of the different SOLDERITE, 22 Creen St., Newark, N. J. parts diagramed in Fig. 4, the connections being exactly the sane.

www.americanradiohistory.com Radio News for April,pril, 1925 1 169 a second grid, which surrounds the plate completely, and shields the first or control re) grid from the plate. It thus makes negli- gible the "capacitive" effect between grid and plate, which CauSCS complications in the use of ordinary tubes for radio-fre- quency amplification. The screen -grid tube, when used as a radio -frequency am- plifier, has this second grid connected to a sit uree of positive voltage, about one- third as high as that applied to the plate. The capacitive effect within the tube is thus reduced to a negligible amount. The action of this tube is otherwise the same as that ACCURATE CAPACITY of the ordinary tube, which has been de- HAMMARLUND scribed. (The. screen -grid has been ex- "Midline" VALUES ASSURED plained in more detail, in the article in CONDENSER Isere is a machine, designed and built by Hanunarlund, February H.tDIO NEWS, mentioned before.) that cuts the slots in which Hamnarlund Condenser Soldered brass plates with tie -bars; plates are firmly soldered. warpless aluminum alloy frame; ball One operation cuts ail slots, thus assuring uniform spac- THE ACCESSORIES bearings; bronze clock -spring pigtail; ing as the first step toward accurate capacity values. full- floating, removable rotor shaft It is such precision methods that have given Hantmar- The tube socket is designed so that the permits direct tandem coupling to lund Condensers world leadership and that guarantee tube may be easily removed from it, in case other condensers. Made in all stand- to you the quality performance for which all Il:uam:tr- ard capacities and accurately matched. lund Products are famous. replacement is necessary, and is equipped Write for Folder with convenient screws for attaching the a6't, pY.Uli/ l. Radio- "lead" wires from the external circuits to HAMMARLUND MFG. CO. the socket; the springs of the sockets in 424 -438 W. 33rd St., New York turn etu;plete the connection to the tube's Canadian Representative âmmarlundPRECIS/ON WHITE RADIO COMPANY, which by wires inside the Ltd. prow/s. lead tube 41 West Ave. N. Hamilton, Ont. PRODUCTS to its elements, respectively. Two prongs in the ordinary tube connect ' S'itJfitin! to the ends of the filament, sometimes des- tatE4 ignated as "plus" and "minus" when in use, and one each to the grid and to the plate. The most common type of socket is the "PC." It is often necessary to have a ÂRT 90 Volt Power socket viiidi is "spring-supported" or "cush- ioned;" so that ringing or "nlicrophonic" noises from tubes are eliminated. Proper Ready? internal construction, resulting in greater Unit :: $12.75 rigidity of the tubes elements, has clone much toward eliminating this effect. Of course! .111 common types of tubes fit into the ordinary "1 -C" steket; lint different tubes require different resistances in series will, the filaments to reduce the voltage applied CARTER to the ends of the filament when using a given "A" voltage, such as that furnished by a storage battery. Resistors of various Adapter Harness types are available for this purpose and may be changed about for the different For Converting tubes, by merely plugging units of the Battery Sets to value proper resistance into the convenient. A.C. Tube Operation Hums, line noises, etc., positively impossible with holders. this new advanced unit. Plug in and forget. Non- Without any structural or acid and noiseless. All detector and intermediate POWER SUPPLIES voltages plainly marked. Simpler to hook up than wiring change in the set. dry cells. Operates any type set I to 12 tubes. As explained before, the filament of a Greater volume and clearness guaranteed. If not thoroughly Change can be made in a satisfied return after using 30 days for complete refund. Win` must be heated; this is done by pass- Guaranteed further 2 years. For 110 -120 volts A.C. 25 to few minutes. Complete, elim- 60 cycle current. 90 volts, 512.75; 112,4. 515.2 î; I35. ing through it a current of the proper 317.50; 157!4, $19.50; 180, 824.00; 202' , $2 0.00. inates "C" batteries. Also built foi D. C. current 110.and 32 volts at only 33.00 value. Various means are used for fur- additional. any size above. Ample stocks -same clay ship- meats. Simply say -ship C.O.D. or write for my Interest- nishing such filament-heating currents; the Write for illustrated folder ing literature, test hnnnials, etc. stornc battery has been widely used and giving full information. the direct current thus furnished is usu- B. HAWLEY SMITH ally very stead- and noiseless. Tubes bave M EIBE Carter Radio Co. R M A GNICAGO 334 Washington Ave. Danbury, Conn., U. S. A.

Station This handy book BUILD YOUR OWN EXPONENTIAL HORN should go with This marvelous 17x21 -In. exponential horn with a 00-In. air column can be WRNY easily built by any ama- NEW YORK every Radio! teur of '' -in. soft wood, 32G METERS -920 KILOCYCLES which produces the most and 2XAL -30.90 METERS It is concerned with null(' wonderful tone quality. pans -their functions-- \Ve furnish you with is owned and operated by the where they are - and .st a set of FULL -SIZED their names. It gives the PATTERNS, which have publishers of titis maga?,ine symbols used in radio been aerurately and hook -ups. so that you scientifically worked out Our Editors will talk to you will be able to read any aerordingto the exponen- diagram and understand tial principle. Simply saw several tomes every week - It. It discusses air waves out the wood to the size -the aerial -then takes and shape of the patterns See .1%(ews you through every radio and nail and glue to- your apex Infra -and finally the gether and you have the for details actual reproduction of latest and sound. MOST EFFICIENT TONE PRODUCER TUNE IN ON This `s a book that Send S2.00 for a set of these hdlalzed patterns and WRNY will give you a lull under- cornDlote i"strurtinns, or wr can furnish you ehr COM- standing of your set. 25c PLETE KIT, rhirh includes the wood cut to itt the n:dla ALL ABOUT RADIO PARTS the glue, our largeslted CONCERT UNIT, and lull Instruct ions. All complete with prepaid for SI LT. 554 X 7 S Inches. fully Illustrated Ask Your Dealer Get any newsstand it from or direct RADIO PRODUCER COMPANY THE CONSRAD COMPANY, INC. 1245 Jefferson Bldg. Peoria. Ill. 230 Fifth Avenue New York City

www.americanradiohistory.com 1170 Radio News for April, 1928

'l1Illllfllq.,p been developed which employ small dry unit consists simply of a transformer-and - Q,'/ batteries; and others which operate from filter arrangement which gives the proper the electric-light socket by means of a shall direct voltages when merely plugged into transformer, which changes the available i mk / %, the house supply. It is possible, therefore, 0/% house -lighting voltage to a low value for - to have a set which is entirely operated ÌI this purpose. The tubes which operate from the light socket, in this manner are very from the light socket. Such sets, although convenient to use, and proper circuit design somewhat more expensive in first cost, are has practically eliminated the troublesome very convenient and economical in the long "hum" occasioned from the rapid changes run; the only replacement needed on such in the direction ( "cycles") of the alternat- sets is the tubes and these should last, with ing current. care, as long as' electric -light bulbs, or con- ««< A still higher voltage must be available siderably more than a year, under conditions the dawning to furnish the potentials necessary on the of ordinary use. plates of the tubes; and this may be de- (An elementary explanation of the more Anew field For men.. rived from "B" batteries, which are simply intricate action of a vacuum tube as a many small "cells" (usually giving 11/2 volts detector will be found in the "I Want to each) all connected in series and enclosed Know" department of this issue of RADIO 3 a suitable container. A "B" socket -power NEWS, on page 1131.) instructive books in PRiCl; Some Suggestions About Resistance $5.00 Coupling 700 Pages WITH advent of better "high- An excellent resistance -coupled amplifier, 500 Illustrations the mu" tubes, reliable resistors and using present -day components, is shown in high- voltage socket -power opera- Fig. 1. It will be noted that, thanks to the Contents of each chapter- ' I. Aircraft Types. II. tion, the resistance- coupled method 30 -mu tubes now available, three stages of Lighter - than - Air Craft. of amplification once more conies into its A.F. are no longer required, provided a IIl. Early Airplane De- signs. General Design own as a means of obtaining excellent tone high -mu detector is employed. Also, it will Considerations. IV. De- quality together with ample volume. be noted that a speaker filter is employed 1 sign and Construction of Aerofoils. V. Arrange- In the first place, the all-important thing (preferably in the form of a choke coil and ment., Fabrication and Bracing of Airplane Wings. VI. is - series -condenser arrangement) to avoid in- Airplane Fuselage and Landing Gear Construction. with resistance coupling to employ high VII. Airplane Power Plant Types and Installation. nm or high amplification tubes. Today, for troducing distortion and also to keep the VIII. Aviation Engine Design and Construction. - direct- current component out of the loud- Air -Cooled Engines. IX. Aviation Engine Design this very purpose, several tubes are avail and Construction. Water-Cooled Engines. X. Avia- able, such as the 240 type, with a mu or speaker. The speaker filter promotes the tion Engine Auxiliaries. XI. Aircraft Propeller use of maximum voltage on the of the Construction and Action. XII. Airplane Equilib- "amplification constant" of 30 as compared plate rium and Control Principles. XIII. Lncrating, Set- with about 7 for the usual 201A type, and power tube, since the plate current does not ting Up and Aligning Airplane. XIV. Inspection and have to flow high- resistance Maintenance of Airplanes and Engines. XV. De- 20 for the high -mu tubes previously avail- through the tails of Modern Airships and Airplanes. XVI. Sea- able. Therefore, the present high -mu tubes winding of the loud speaker, as it must planes, Flying Boats, Amphibians and Other Air- when is connected directly the craft. XVII. Some Aspects of Commercial Aviation. give a step -up effect 50 per cent. greater; the latter to XVIII. Aircraft Instruments and Aerial Navigation. which is essential in a system in which the amplifier output. XIX. Standard Nomenclature for Aeronautics Report No. 240, Part I. amplification is solely a function of the This book is written in simple, understandable tube, without the step -up transformer to RESISTANCE VALUES language. help out, as in transformer- coupled am- The resistance values indicated in the fig- AVIATION plification. ure do not run as high, in the case of the ENGINES grid leaks, as those usually specified for SELECTION OF RESISTORS This treatise, written by a the present high -mu tubes. While there is recognized authority on all The second consideration is the use of volume, which is of the practical aspects of a slight loss in certainly internal combustion engine proper resistors; not only in the matter of not noticeable, there is better assurance of a construction, maintenance. and repair, fills the need correct values, but particularly in assuring grid leakage ample to avoid any possibility as no other book does. rite matter is logically stability of operation. Resistance coupling of "blocking" or the piling up of successive arranged; all descriptive mat- ter is simply expressed and is particularly susceptible to changes in re- signals. copiously Illustrated, so that sistance, which the and some- anyone can understand air- alter results The layout shown in Fig. 1, comprising a »tane engine operation and times introduce serious noises. For this 30-mu tube for the detector, a 30-nm tube repair even if without re- sious mechanical training. reason it is desirable to employ heavy -duty for the first stage, and a 171 or 210 -type of This work is invaluable for anyone desiring to become resistors which are capable of providing ac- power tube for the second stage, will pro- an aviator or aviator mechan- ician. curate and lasting resistance values, even vide ample volume, with a tone quality when with- 274 PACES PRICE $1.25 handling considerable currents, noticeably better than the average trans- out [langer of resistance changes to cause former and at comparatively low cost. A. B. C. OF noises. The third consideration, and one of great 0.F. CnOHE AVIATION .0.mf. .ormf. importance, is to have available sufficient 240 .1 240 210 This book describes the basic / principles of aviation, tells plate voltage. It is often overlooked that, how a balloon, or dirigible is made, and why it floats in the in resistance coupling, the voltage impressed air. Describes how an airplane Hies. It shows in detail the on the plate of the tube must pass through different parts of an airplane. what they are, and what they the plate-coupling resistor, the value of do. Describes all types of air- which is usially 100,000 ohms and over; in planes and how they differ in construction, as well as de- the case of the 30 -mu tube, the plate - tailing the advantages and ,iv. A.C. disadvantages of different coupling resistor is of 250,000 ohms. Obvi- types of aircraft. It includes a complete dictionary of avia- ously, to overcome this high resistance in the tion terms and clear drawings of leading airplanes. circuit and still have sufficient voltage to FIG. I --q. $ B.190 8*500 the tube efficiently, it is necessary operate A two-stage resistance- coupled amplifier, using PRICEI$1.25 to start out with high voltage (preferably "high -mu" tubes. Remit by cash; stamps, check, or money order 180 volts) on the plate -coupling resistor, or No C.O.D.'s at the maximum-voltage tap of the usual The use of a high -mu detector tube serves radio power unit. If "B" batteries are em- to obtain considerable amplification as well We Pay Postage On All Books ployed, there should be four blocks, of 45 as signal rectification. A 3- megohm metal - volts each and of the heavy -duty type, to ized resistor should be employed for the CONSRAD COMPANY, Inc. provide the necessary current over a long detector grid leak, in combination with a 230 FIFTH AVENUE NEW YORK period of service. .00025 -mf. grid condenser.

www.americanradiohistory.com Radio News for Apri!, 1928 1171

PUSII-PULL CIRCUIT For those seeking enormous volume, to- gether with a remarkable depth and detail The distance, about 8,000 miles, of tone, resistance coupling presents many Seattle and Australia Talk; Is the longest over which a two - interesting possibilities in conjunction with World's Radio Phone Record way conversation ever has been present -day high- voltage,socket- power oper- conducted. It is all the more re- ation. In Fig. 2 we present an interesting markable because the power was Special to The New York Tisnes. development in the way of a powerful push - only 100 watts. Most broadcasters, pull amplifier, with excellent tone quality SEATTLE, Wash., July 2. -Ra- with ranges of a few hundred in conjunction with a good speaker capable dio telephone communication has miles, use from 1,000 to 5,000 of handling the full volt le. Indeed, this been established between Seattle watts. The wave length of both amplifier provides the volume of a small and Australia, setting a new world Seattle and Australian} stations orchestra, with a realism that is quite start- distance record. This was an- was 38 meters. ling, even to blasé radio enthusiasts. The nounced today by Frederick G. cost of this amplifier is surprisingly low. Simpson, Seattle engineer and With resistance coupling employed in this owner of Station 7XF in the manner, we remove the possibility of over- Grand Trunk Dock. loaded tubes and therefore the last vestige A two -hour voice conversation Mr. Simpson was using a Standard of distortion in power amplification. was held by E. J. Lesser, manager Item 35 as listed in Bulletin 237D. of the Simpson Radio Corpora- Write for your copy of this bulletin tion, and J. W. Robinson, an Aus- today. tralian amateur. Robinson lives at Concord, about 200 miles from Brisbane, His station is 2RN.

D z ELECTRIC SPECIALTY COMPANY Trade "ESCO" Mark 211 South Street Stamford, Conn., U. S. A

Makers of Motor Generators and Dynamotor, with the least ripple and the most mites per watt.

Complete details of a circuit applying the ad Vantages of push -pall action to a resistance. rot pled amplifier. The constants pima, may be modified by experiment. A. C. OPERATION! The diagram is virtually self-explanatory. It is best to use 25/2-watt power resistors for the 8,000 -olun units employed in coupling HE Type 440 -A Transformer illustrated is the output to the loud speaker, in order to designed for use on 105 -125 V. (50 -60 cycle) handle the considerable current without ma- I A. C., is rated 65 watts. The following terial change of resistance value. Because and at of the power handled with this amplifier, voltages and currents are available: none but reliable resistors can be employed. 2 Volts 10 Amperes et 3.5 " 5 POWER UNIT It 5 " 25 It will be noted that the power must be 2 supplied by at radio power unit capable of 7.5 " delivering 425 volts for the plate circuits Type 440 -A Transformer nui 7/ volts A.C. for the filaments of the Price-240.00 large tubes. One 216 -B -type rectifier tube The use of this transformer, together with the new A. C. tubes, and a will be rather heavily taxed if made to the General Radio type 445 supply two 210 -type power tubes, and the dependable plate supply unit such as plate voltage is apt tu drop below the value Plate Supply and Grid Bias Unit, makes the conversion of a battery - necessary to operate these tubes at proper operated receiver into one operated from the light socket very simple. efficiency. A 281 -type rectifier, substituted If you do not care to undertake this change yourself, go to your for the usual 216 -11, will help out in this con- community set builder. He is well qualified to serve you. nection. However, for best results the radio power milt should have two 216 -B or 281 - type rectifiers arranged for full -wave recti- GENERAL RADIO CO. fication, which will supply ample plate volt- Write for Bulletin No. '129 age and current for the operation of two STREET CAMBRIDGE, MASS. 210 -type power tubes. 30 STATE If we change the "C" battery to 45 volts and the plate voltage to 200, with the output plate resistors 5,0(K) ohms catch, good results $100 WILL SAVE YOUR will be obtained with two 171 tubes in place CV, oßóannr SPEAKER of the 210 tidies, for those who oust Oper- i The Craftsman Dollar ate on "B" batteries or on moderate voltage Speaker Filter is Guaran- teed to relieve your speaker radio power units. 3pantamazaag, of the DC plate current

from big y (up to 250 volts). It gives While the values given in these diagrams maker loth successfulue ter speaker a chance to oper- year.. All Battery have been found highly satisfactory, there consolersor0 trisiprs. ate at its best. Attached Msets.`oa'tbarbetasas daysa in a second. Send collar is considerable selecble aty.2 isa Urn.rimes lug room for variation. and eich.for athedray, bill NOW! and ach. oliilra to,tono. Turnt dial for Incidentally, in Fig. 2 we have Y,( Il d. fully , comOtC-ed etsem not indi- ÌJed, fully,pmmot.aA eebi CRAFTSMAN RADIO PRODUCTS woo hmi ,o +ernste cated the ti lament- supply current, but it ON t0 R 9 Orchard St. Newark, N. J. goes without saying that the first -stage tubes User MIDWEgñMIDWEST RADIO CORPORATION DAjenrs 404DMhacoSidg.Cincinnatl o aire of the 240 type, operating on 5 volts of battery current, while the two power tubes CONDENSERS and are operated on either 7y, volts raw A.C. $21 WARREN For I to 10 tubes. Complete with folio. VERITAS RESISTORS if of the 210 type, or 5 volts raw A.C. or (iunran teed. tvtio $83. Now DII? ECT Stand up on their Jobs battery, if of the 171 type. to you. 521.00. Write: "-oho Deutschmann Co., Cambridge. Mass. WARREN ELECTRIC CO.. Dept. R.N., Peoria1,111

www.americanradiohistory.com 1172 Radio News for April, 1928

and Republocrats alike. It comes from the hasty, though oracular, state of Oklahoma. Radio "Bugs" Audie Robertson of Alex, Okla., is the dis- Conner coverer. WHAT is, probably, the best "bug" Cabinets Which the intrepid explorers of Radio Lanci have discovered for the edification of REDUCED our readers is given below; and the sceptic Entire factory stock of Conner Convert. who cares to trace the lines will find it a Tent Cabinets now being closed out at real circuit. The contributing entomologist, 25% REDUCTION Prices NOW $26.25 to $74.75 Jacobean, Renaissance and Sheraton designs, done in beautifully high- lighted walnut and ma- hogany. Fronts open down into convenient "The Younger Generation -Whereto on Roller desks. Write today for Skates ? ' illustrations. A Conner Cabinet assembles every detail Madison, Wis., is a co- educationally -col- of your receiving set, batteries and ac- legiate city, and affords opportunity for the cessories, in a scientifically convenient observance of coruscating youth at the most arrangement and encloses everything in an exceptionally beautiful piece of period plastic period. We may suppose, therefore, furniture. You can secure one at this that this couple have been drawn from life emergency bargain price if you act quick- by James W. McGrath of that city. ly. Write today for illustrations and The DX Hound is famous in radio lore, details. but his habits are distinctly nocturnal, so that he has hitherto escaped observation. CONNER RADIO CABINET CO. Francis D. Johnston of Pittsburgh, chooses the somewhat intriguing title: "A Dry -Bat- New Albany, Indiana tery Manufacturer's Impression of a 'B' 'Eliminator.'" >l:41 "A Lightning Kick on the Grid- Iron" is 9{ )th the title selected by P. Beck of Herrick, Ill., ^----d+ FROSTRADIO for this scene of action. It seems to us,

GEM RHEOSTATS The animal, however, has been drawn dur- will like Frost Gem ing a brief moment of hesitation while stalk- yOURheostats the minute you set eyes on them. They are ing his prey. "A true specimen," comments what you have always W. wanted -nighty good small Joseph Sine of Salt Lake City. "Ob- Mania's. Metal frame con- serve the distance- struction. with resistance getting nose, the crystal- clement securely wound on line ears and, last but not least, his flexible Bakelite strip. Gem tales, Rheostats are Ifi inches which pass all understanding." in diameter. Supplied in wide variety of resistances Carl Sipe of Anderson, Incl., pictures a from 3 to 30 ohms, and as parade 200 and 400 ohm poten- of the Thoriated Soldiers, which tiometers. Also made with Moment switch at slight extra cost. Use switch, 75e. With switch, 51.00. 41 G7 [ROSI -RADIO 'hlh9idM9 n?ni,N?gmu9hbt, Mail Coupon for Two Frost Booklets however, that this terrific kick is being be- Fill out and mail coupon below and we will send you stowed on the filament, which may not sur- FREE the two Alost Booklets "What Set Shall I Build?" and "For Better Reception." vive the indignity. é. HERBERT H. FROST, INC. At the right is a grim hunter; we might Main Offices and Factory: have been at a loss to name him, but Jack- hardly needs the brief explanation: ' "l'he Elkhart, Ind. son Edwards of Tucson, Ariz., supplies the Nine -in- Line." Long leads are evidently Chicago New York City data: 'This is a Lou Pantenna, found only conspicuous by their absence. in A. J. Manson of Nelson, B. C., pictures a HERBERT H. FROST. Inc. the wilds of Laboratoria. His eyes can 160 North LaSalle Street, Chicago, III. detect anything, and he is holding a Peri- pair whom we took at first glimpse for The Please send me free your two booklets, as adver- Heavenly Twins. The legend informs us tised in Radio News for April. dyne, a weapon against the tribe of Poo Name Receptionia." Whether or not the political events of the Street Address 'CLe lZA $ year will confute the prophets, time alone ELI " city State

Wholesale Radio Calaloat ldo -got Ch FREE+eater-Set Builders! Save Money! Send for this book of bargains. Everything in Radio -all the newest hook -ups. Sets, kits, parts, cabinets, consoles and sup- plies. If you want the-best for the least money, you need this catalog. SHURE RADIO COMPANY 329-D West Madison St. Chicago, Ill, :QuAoR: ]E1LKA\y of their full names: "Clarifier and Elimi- nator get good reception" and Suppressors are made by The Langbein- Kaufman Radio Co. (Dept. N). 62 Franklin Some of our bugs are far from home; this St.. New Haven, Conn. Write for prices and spirited with Tilden on the left and tables of values. scene, can tell. This sketch of "A Broad -Tuning Suzanne on the right, comes from A. Haer- Receiver," however, will appeal to Demicans tel of Offenbach, Germany. But while Herr

www.americanradiohistory.com 1173 Radio News for April, 1928 Watch the Last Stage ALARGE percentage of the distortion, in most radio receivers, is caused by overloading the tube in the last stage of audio amplification. When tubes of the 201A or 112 type are used, the only ways to reduce the distortion may be to substi- tute a burger tube or to decrease the vol - Used in uoa; but with tubes of the 171 and 210 Every High Grade Circuit distortion can usually be remedied liaertel is fair DX, he is not to be com- types, the Receiver Today! the grid -bias voltage or pared with the two which close our sym- by correctly adjusting INCLUDING on the stage. The in- posium. ( "C" 'battery) last Strobolyne, Loftin- \Vldte Constant Coupled, Quailtonr 6. which are packed with the Improved Aristocrat, Oliver Lodge Best's Super-Hemero- E. G. Castro of Manila (Philippine struction sheets, dyne. 13-T Power Six. Hammarlund- Roberts. Daily News give approximately values of grid - 4, World's Record Super, Goodwin Aperiadie Detector Islands), sends in "The I-Innis Covered tube, Circuit. Quadraformer 6, Best's 1927, Silver's Knockout. suitable for use with various and many others. Wagon." Whether it is drawn by a broncho bias voltage plate potentials; hut, in order to stake sure MODEL "N" is VARIO- DENSER that the tube is not being overloaded, it Micrometer ad- connect it ntilliammeter in the justment easily necessary to made, assures ex- plate circuit of the last tube. act oscillation con- trol. Quick. easy If there is no appreciable movement of tuning. more vol- ume, clearness and Model O the needle of the millianunetcr when loud stability. Capacity MODEL "G" VARIO- DENSER is cor- range 1.5 to 20 signals are being received, the grid micro - micro fa- rectly biased. On the other hand, when the rads. Price $1.00. Obtains the proper grid capacity on needle of the meter oscillates as the intensit7, Cockaday circuits, later and inter- is increased, the tube is being mediate frequency tuning in uPer- of the signal heterodyne and positive grid bias In and the bias must be increased all sets. Three variable capacltY or a towable, we cannot say; _hut it is evi- overloaded ranges. Price complete, with grid dently on its westward way. or decreased, as the case may be. If it is clips, 51.50. oscil- X -L NEW BAKELITE INSULATED A companion piece shows the effect of impossible to prevent the needle from PUSH POSTS progress. 'l'hc radio automobile is the work lating by any adjustment of the grid bias, The perfect binding post at last! Convenient. simple: Permanent connections. You don't have to remember of a fellow -Filipino, Enrique G. Hinlo of titis filet indicates that too much volume is to tighten then[. Push down the X-L. insert wire, amplifier. remove pressure. Connection is tight and will rrny Manopla, Occ. Negro. Pending returns from being obtained from the tight. No vibrations can loosen. Releases Instantly. The meter used for this purpose should Standard markinia. or boxed in complete sets. Price each, 15 cents. have a range from 0 to 25 milliamperes, and new up-to -due honk of wiring diagram the maximum fluctuation of the plate cur- FREEBigof all lending circuits. Write today for ropy. Investigate the Goodwin Aperlodlc Circuit. This Is rent should not he greater than 10% of the applicable to any set and adds a stage without added total current. In the case of the 171 -type tuning controls. tube, the plate current should be 20 mil- X -L RADIO LABORATORIES liamperes with a plate potential of 180 2426 Lincoln Ave., Chicago, I I1. r Kerguelen, Ma mua rie Island, and the South volts, and the correct grid bias is approxi- Shetlands, we award to these contributors mately 1.0 volts. With the 210 tube, operat- the prizes for greatest distance covered by ing with a plate potential of 425 volts, the transmission. proper plate current is 18 milliamperes, and '.-ïç, ,a Entomologists, the grid -bias potential approximately 35 . for your labors in the ,Gi. tij Í cause of radio science, and on behalf of volts. PERlTE the radio public-your public -we thank wal.`ch Dog you! of%our A FILAMENT ELIMINATOR Ji r9, Use of Separate Amplifier . r)ubes There WU s a I/Ounq radio student Who was told to be careful, hut wouldn't; TIIEUE is no unanswerable reason why On "rl+" he placed the audio -frequency amplifier of a re- "B 90" in haste- ceiving installation should be built as part Then he tried to tune in, and he couldn't! of the radio set; while, on the other hand, -J. Hope. it is often more satisfactory to construct it as a separate unit. The practice of com- Simplifies- TUNING bining the audio amplifier with the "B" 1. Tube control-No knobs OUT 2. Wiring -Short leads His voice was fall of static socket -power unit is now becoming very - and has received the endorsement 3. Panel design -No drilling "0h, cant you learn to carer common, a of radio engineers. 4. Tuning -No hand rheostats Her answer rcag emphatic: of large number With the amplifier and "13" supply de- Only AMPERITE can automatically keep the tern. Said .rhe, "Oct oaf the air!" perature or voltage of the filament constant despite -Dorothy Porenall. vice in one unit, the installation is much variations in "A" battery voltage. Particularly es- may be sential with eliminators. Proved for 6 years to be more flexible; as it connected indispensable in every radio circuit. Do not con- RADIO TERM ILLUSTRATED quickly and easily with any type of either fuse with fixed filament resistors. Accept only mi- AMPERITE. Price 51.10 with mounting(inU.S.A.). radio set, phonograph pick -up unit, or At all dealers. crophone. In addition, this prevents the Write for Free "Amperite Book" of season's beat circuits necessity of rebuilding the audio amplifier and latest construction data. Address Lila. AN-4 every time one builds a new set, and elimi- Radiali Co.. 50 Franklin St., New York nates the danger involved in having exposed high-tension wires between the "B "- supply unit and the power tube. PERITE The reproduction obtained will be no less `Jhe "SELF-ADJUSTING "Rheostat satisfactory when an external amplifier is used, provided one simple precaution is taken in the design of the receiver; i.e., an H.P. choke coil and a by -pass condenser must be connected in the plate circuit of the detector tube. The by -pass condenser To Dealers-New. illustrated should have a capacity of approximately Wholesale Radio Catalog gives loom .001 -mf. and be connected between the de- sets. Features master-built sing) control radii tector plate and the "A lead. The B.F. sets for both battery and all-electric operation. -" Full showing of "A" and "B" Eliminators and choke coil should be mounted near the de- thousands of other great values. Write on busl- neas letter-head for this free hook today. tector tube and connected directly in series HAMILTON -CARR RADIO CORPORATION "A Control Switch." with the lead to the A.F. amplifier. 711 West take St.. Dept. 396, Chicago, 111.

www.americanradiohistory.com Radio News for April, 1928 An R. F. Short-Wave Broadcast Receiver

(Continued fron putte 1130)

operating on wavelengths between 10 and C3-One S.L.F. variable condenser, .00025 - 550 meters. Six different types of coils and mf.; two coils of each type (12 coils in all) are C4-One mica fixed condenser, .00025-mf.; needed to cover this wide band. However, T1-One A.F. transformer, 3:1 ratio; all the coils are not required if the builder 'r2 -One A.F. transformer, push -pull input wishes to limit the wavelength range of the type; set to a narrower band. The waveband '1'3 -One A.F. choke coil, push -pull output which each of the six coils covers approxi- type; mately is as follows: coil No. 1, 10 to 25 RI-One grid leak, 5- megohm; meters; coil No. 2, 15 to 33.5 meters; coil R2, R3, R4 -Three filament- ballast units, 5- No. 3, 31.5 to 68 meters; coil No. 4, 57 to volt, 1/4-amp. type; 133 meters; coil No. 5, 125 to 250 meters R5-One filament -ballast unit, 5 -volt, I/.- and coil No. 6, 235 to 550 meters. If it is amp. type; desired to increase the wavelength range of R6 -One 500,000 -ohm volume- control rheo- the set to 725 meters it is possible to do so stat and filament switch; by connecting a .0001 -mf. mica fixed con- RFC -One R.F. choke coil, 60- millihenry; denser in shunt with each of the tuning con- PII -One oscillation control, variable re- densers (CI and C2) when coil No. 0 is be- sistor- condenser type; ing used. VI, V2, V3 -Three vacuum tubes, 201A- In constructing the coils the secondary type; windings must be spaced. The chart in the V4, V5 -Two power tubes, 171A -type; drawing gives the number of turns, the size SW -One jack switch, D.P.D.T. type; of wire and the length of each secondary Three tuning dials, vernier type; 1EYF winding; and with this data the builder can Five vacuum -tube sockets, L'-\' -type; determine the proper spacing between turns One panel, 7 x 24 x 3/16 inches; by experiment. The tickler and primary One sub- panel, 7 x 23 x 3/10 inches; NOOkiUP coils are wound with insulated wire and are Three brackets, 3 inches high; not spaced. The primary coil consists of 'twelve binding posts; ,10 turns of No. 24 S.S.C. wire wound on a Two coil mountings (see drawing for de- The new form 21/a inches in diameter. The tickler tails). improved coils are merely glued inside the secondaries, or held in place with a few drops of sealing FREE BLUEPRINTS Consrad Pattern Book wax or paraffin from a candle. The Strobodyne, the most sensational The following is a complete list 'of the A set of full -size blueprints, covering all development of the age, is the greatest parts required for the construction of this the constructional details of the flexible Super-Heterodyne ever designed. The short -wave receiving set: short -wave receiver described in the fore- best known features of Radio construc- going article, may be obtained free of tion have been incorporated in this LIST OF PARTS charge at the office of RADIO NEWS, 230 amazing circuit. LI, L2 -Two sets of coils (see drawing for Fifth Avenue, New York City. Readers de- And Consrad, the famous Pattern details) ; siring to have these prints delivered by mail publishers of Radio, have printed the CI, C2-'two S.L.F. variable condensers, should send ten cents in stamps or coin to entire constructional details for this .00014-inf. ; cover the cost of mailing. ultimate development in up-to -date Radio efficiency in a new and most convenient form. The new Consrad creation, a handsomely -bound booklet, contains all the details in complete simplified form. Short -Wave Broadcast Information In this Pattern Book are four complete, full -size blueprints and all necessary By E. T. Somerset (England) constructional data required for as- sembling the Strobodyne- step -by- step instruction. IN view of the difficulty experienced by the set bursts into oscillation after a sta- most people in obtaining a comprehensive tion has been tuned in and the hands re- Write now -get your Pattern Book- list of short -wave radio -telephone stations, moved from the dials) this may almost cer- you will enjoy building this marvelous and the fact that a large number of the tainly be cured by inserting an extra R.F. will results circuit -you enjoy the readers of RADIO NEWS have constructed choke in series with that used already; and which are sure to be yours with this by-passing epoch of radio development -the the short -wave broadcast receiver featured the second choke to "A-" with STROBODYNE. by this magazine, the writer has compiled a .0005 -mf. fixed condenser on each side. the list of stations given below, grouped If there is trouble with body-capacity THE CONSRAD CO., INC. into three divisions, corresponding to the effects, however slight, an improvement 230 Fifth Ave. New York City tuning coil which must be used with that can always be obtained by taking a sepa- waveband. rate ground lead direct from the "A -" Of course it must be realized that the battery terminal to the ground binding post THE CONSRAD CO., INC. bands overlap; for instance, 2XAF may on the set, and also by grounding the fila- 230 Fifth Ave., New York City be found to come in at the extreme upper ment end of the grid inductor. Cent lernen: end of the scale with No. 1 coil, as well The following list is, of course, subject Enclosed Please find 50e, for which please send me the Consrad Pattern Book for the as at the lower end of No. 2. This is ex- to changes, as these transmissions are STROI3ODY NE. plained also by the fact that different tubes largely experimental; by the time it ap- Name and detector voltages will cause an altera- pears, \VJ7, will probably be operating on tion in readings. 22.207 and 18.715 meters. Likewise, Nor - Addre:, Should the reader be unfortunate enough wau's and Denmark's short -wave transmit- City ...State ... to experience trouble with what is known ters will be on the air, and as well PCJJ, as "Threshold Oscillation" (that is to say, which has been removed from Eindhoven;

www.americanradiohistory.com Radio News for April, 1928 117 but the wavelengths are not at present Konigsvusterhausen, Germany 52.00 Cincinnati, Ohio (\\-LW) 52.02 definitely known. Brooklyn, N. Y 54.00 Meters Columbus, Ohio 54.02 Ocean Township, N. J. ( \ \XI') 13.88 Melbourne, Australia OAR/ 55.00 They make Rocky Point, N. Y. (2X1 i `i 16.02 Nauen, Germany (. \GJ) 56.70 Ilamlueng, Java (.\ N I 11 17.00 Round Brook, N. J. (3X11) 60.00 Merlin, Germany (.\GC) 17.20 Council Bluffs, Iowa (ONU) 61.06 17.40 .Malabar, Jaca East Pittsburgh, I 'a. ( KI)E. \) 62.50 Eootwijk, Ilulhunl (ICI.!.) (beam I.. 18.70 Richmond I1 ill, N. Y. (WA BC) 64.00 Schenectady, N. V. (2X. \It1 21.96 Newark, X. J. (IXI :. \) 65.18 Richmond hill. N. V. (!X t:1 22.10 Inglewood, Calif. (6X. \1) 66.04 22.80 $6,000 Fort Wayne, Indiana Coil No. 3 (57 -133 meters) ) 23.00 I loulton, Maine (2NA. \' Perth, Australia (6 \V F) 100.00 Chelmsford, England (5S \\') 24.00 Spokane. \ \'ash. (7N A ll) 105.90 a year Pittsburgh, Pa. (IODNA) 27.00 Richmond Ilill, N. Y. (2X E) 106.00 Sydney, Australia (2\IN) 28.50 l.os Angeles, Calif. (6X BR) (portable) 106.00 Hilversum, Ilollunl (PCJJ) 30.20 Tilton, New (Hampshire (IX\ ) 109.00 The facts prove that (Temporarily silent ) 'Transatlantic phone. Sew York, N. Y. (2X. \I.) 30.00 YOU can achieve Cerne, Switzerland (Ell 9 I )(' 1 32.00 Sydney, Australia WC) 32.00 32.00 Success Radio! Drummondville, Canada (CI') WEATHER BROADCASTS FROM NAA in Zurich, Switzerland (Ell 9X1)) 32.00 Johannesburg, Su. Africa (1 II) 32.00 On February 1 the U. S. Weather Bureau began Radio News writes us: Caterham, England (2N31) 32.50 a series of dally transmissions, in Morse cotte, from Coil No. 2 (31.5--68 meters) the high -power radio station at Arlington, Va., by "In looking over the dealer mail received Schenectady, N. Y. (2X AI') 32.77 means of remote control. These schedules arc as San Francisco, Calif. (6X AR) 33.00 follows, in Eastern Standard Time: in the last three months we find that the .Malabar, Java 33.00 8:15 a. m, on 74.7, 37.4 and 24.9 meters. average income of all dealers who gave Melbourne, Australia (31.1)) 36.00 10:00 a, nt. on 2,677 and 18.6 meters. Tomsk, Siberia (RA19) 37.00 11:00 a. tn. on 24.9 meters, us their income figures, 38 in number, Paris, France (Radio -Vitus) 37.00 8:15 p. m. on 74.7 meters. Taipeh, Formosa. Japan (J FA II) 39.50 10:110 p. nt, on 8?,18 and 2,677 meters. averages more than $6,000 a year." Lyons, France (Radio Lyons) 40.00 11:00 p. nt, on 74.7 meters, los Angeles, Calif. (6X BR) (Portable) 10.00 The 8:15 broadcasts, morning and evening, are (Signed) C. W. EMERSON Stuttgart, Germany 42.00 in the regular Weather linreati code: those at Pittsburgh, Pa, (KOK.\) 42.95 11:00 in the International code, especially for the ' RADIO NEWS New Brunswick. N. J. ( \VIZ) 43.35 use of European weather bureaus, and are re- langenberg. Germany (I..\ 1 43.90 peated front the Eiffel Tower in Paris. Further Rome, Italy, (1. \X) -15.00 details may be obtained directly from the Weather Why don't you think this over and Ocean Tp., N. J. (WNW') 46.48 I lurr:un. say to yourself, "These dealers are no smarter than I am. If I knew radio thoroughly, I could make that much and more. I know that the Radio In- stitute of America is America's oldest Short -Wave Data Wanted radio school-that it gives the fin- RADM salirons in nonne parts of the stations they may hear; giving the wave- est radio instruction obtainable any- world are now broadcasting on short lengths as closely as they can guess the fig- where, and the finest and fullest radio wavelengths (i.e., below 200 oneter s); hut ures from the dial settings, by comparing because most of their transmissions are still the latter with the settings for such con- equipment. only of experimental nature, RADIO NEWS sistent transmitters as KDKA, WGY and "I know that RIA is conducted by has found it difficult to obtain, even from \1-L \\'. These reports can be \written con- the stations themselves, accurate informa- veniently on the backs of postcards. the Radio Corporation of America tion about their operating fregncnciis, IR.uno Nt :ws will publish the data it re- and is backed by General Electric and hours of broadcasting, rte. Readers own- ceives, for the benefit of the many people Westinghouse-that their course in ing short -wave receivers are therefore re- who have built short -weave receivers and radio is complete and entirely covers quested to report to 11.\IIIt) Nt:w-s any wish to be informed about everything they including op- strange short-wave I"oadeaut (not code) can expect to hear with them. every phase of radio, erating, broadcasting, in fact every- thing in radio. I know that I can make progress because everything is told Convenient Phonograph Socket Wholesale Radio Lawsuit so clearly. I can get this instruction A FAN who ttttcntpts to use the studio AN unusual scene was staged recently in at home, and prepare for success in L circuit of his radio receiver as an " to London courtroom, when a large in- radio without giving up my present stallment house dealing amplifier for phonograph music often finds in radio and other job. I can study when I please and as it inconvenient to reunove the detector tube equipment brought suit against 511 of its each time he desires to insert the plug froua customers who had entered into "hire-pur- long as I please. With the tremendous the pick -up unit in the detector socket. This chase" agreements, for balancis due, vary- opportunities opening up in radio may be avoided by umunting an additional ing from five shillings ($1.25) up to five today, I certainly can't t'acouut -taie socket on the baseboard of the pounds ). Judgments were given by pass up this opportun- set, and connecting it in pareellel with the the presiding magistrate for payments in ity to learn more about detector socket. With the receiver ar- monthly amounts, varying from two shil- ranged in this manner it is necessary only lings (.50 cents) up, according to the cir- the RIA course. Here's to turn out the filaments of the detector cumstances of the defendants. one coupon I will clip. and 11.1". topes, by menons of a rheostat on I want the full facts." the front panel, and insert the plug from Tears"! the coupon and mail it now. the phonograph in the extra socket. An Obliging Radio Artist RADIO INSTITUTE OF AItIERICA Dept. A -4 326 Broadway, New York City 'T'IIE Stmdnan," who carries sleep to millions of eyes, is a 1 tired little very RADIO INSTITUTE OF AMERICA, Dept. A -4 Special Sets for Navy real individual to the wee folks in and around 326 Broadway, New York City T(I prevent its seaplanes when forced Itrishanc, .\n.dr,iliti, where he broadcasts at Dear Mr. Duncan: down in (light from being without means times over the local station. More Please send me your new catalog. I want to than know more about your new radio course. of communication, the United States Navy that, "he can sometimes he seen perched on will equip them with short-wave transmit- the top of 4ft)G with a small searchlight, Nasse ters lan\ing hand -driven generators for an signalling to his little radio friends. In re- Address emergency. The standard frequency will be turn, the youngsters acknowledge `Sandy's' 8,770 kilocycles, corresponding to 34.19 greeting by weaving lights, indicating that Meters. they have spotted the signals."

www.americanradiohistory.com 117c) Radio News for April, 1928 Metering The Popularity New AERO Circuits of Programs For Either Battery IT has often been asserted that the multi- plicity of aerials in a modern city weak- or A. C. Operation ens the field strength of a broadcast station by their absorption effect, when all are Proper constants for A. C. operation of the tuned in to its wave; and some time ago improved Aero-Dyne 6 and the Aero Seven have been studied out, and these excellent circuits are test experiments were carried on in the now adaptable to either A. C. or battery opera- suburbs of London by British investigators, tion. A. C. blueprints are packed in foundation units. They may also be obtained by sending who reported confirmation of these theories. 25c for each direct to the factory. It is true that in the United States the studies of station field strength have shown a much greater influence upon broadcast waves by the huge masses of steel and net- works of electric wires in urban centers. The English engineers are now debating SOMETHING NEW more or less seriously the question whether, MAIL if a "load indicator" could be devised, show- AERO Universal Tuned Radio Frequency Kit ing the output load on a broadcast station's YOUR Especially designed for the Improved Aero- aerial, it would not be possible to determine Dyne 6. Kit consists of 4 twice- matched units. Adaptable to 201 -A, 199, 112, and the the popularity of a program, locally at least, ORDER new 240 and A. C. tubes. Tuning range be- by the number of nearby antennas tuned to low 200 to above 550 meters. its frequency and absorbing power. This kit will make any circuit better in selec- tivity, tone and range. Will eliminate losses This would indeed be a welcome gadget and give the greatest receiving efficiency. for the station owner, and solve by elimina- Code No. U- 16 (for .0005 Cond.) $15.00 Code No. U -I63 (for .00035 Cond.) 15.00 tion the problem of luring the elusive "ap- plause card" from the coy listener; but, un- fortunately, it must be added, no such indi- cator has vet been invented. There is an opportunity for our ingenious readers, who are always discovering new hook -ups; but we will have to stipulate that plans and specifications for such a device must be ac- AERO Seven Tuned Radio Frequency Kit companied by a working model before they A Radio Trade Paper Especially designed for the Aero 7. Kit consists are considered seriously at the office of by of 3 twice- matched units. Coils are wound on RADIO NEWS. Edited You and For You Bakelite skeleton forms, assuring a 95 per cent air di-electric. Tuning range from below 200 to above 500 meters. Adaptable to 201-A, 199, the latest trends of 112, and the new 240 and A. C. tubes. ALL Code No. U- 12 (for .0005 Cond.) $12.00 the industry - modern Code No. U -123 (for .00035 Cond.) 12.00 HAUNTED! merchandising methods use in tuned - NOTE-All .4ERO Universal Kits for "You haven't forgotten Freddy, then ?" radio frequency circuits hare pocked in each toil with proven sales building prac- a aced primary a twice matched calibration slip chewing "No, no, even though we've parted for- reading of ruck fired primary AERO Unircrsal COU at 250 and 500 meters: all having an accurate and similar ever I still can hear his voice in the still tices that have been actually calibration. Be sure to keep these slips. They're salvable if you decide to add batter R. F. stage to your set. watches of the night." tested by brother dealers - "Ali, that is the curse of memory." a complete merchandising A NEW SERVICE "Not at all, silly; it's the curse of having We have arranged to furnish the home set builder service, having for its back- with complete Foundation Units for the above loved a radio announcer !"-Gleason Pease. named Circuits, drilled and engraved on Westing- ground years of experience house \licarta. Detailed blueprints for both battery and A. C. operation and wiring diagram with both dealers and fans. for each circuit included with every foundation unit free. Write for information and prices. ALL BUT ONE THING This is what RADIO NEWS You should be able to get any of the above Aero Coils and parts from your dealer. If DEALERS PERSONAL EDI- he should be out of stock order direct from the factory. TION gives you. Be sure and mail your order now. AERO PRODUCTS, Inc. It means bigger business - Dept. 105 bigger profits. 1772 Wilson Ave. Chicago, Ill. Regular price $2.50 (yearly subscrip- tion). Special offer brings _ 1 1 ® this remarkable service to you for $1.50. BIG RADIO CATALOG ? From the "Big, Friendly ATTACH YOUR LETTERHEAD! Radio House" NEw 1928 nook poses finest, newest wcü -knows sets :parst, 11114 eliminators, accessories at lowest Vices. DEALERS WRITE FOR THIS CATALOG! EXPERIMENTER PUBLISHING CO. 230 Fifth Ave., New York City Gentlemen: Kindly send me the Radio News-Dealers Persona' Edition, for one year, beginning with the next issue. I am enclosing check for one dollar and fifty cents to cover. WeSternRadi014100. This I understand is a special reduced price, two dollars 126 West Lake St., Dept. 14, Chicago, III. and fifty cents being the regular subscription rate. Name RAISE BELGIAN HARES Address New Zealand Reds - Chinchillas - Flemish Grants MAKE BIC MONEY -Wt Supply Stock and following blew for "Now, my dear, do you understand how the City State l.,un fine nl Rd°$raise: set works?" -Cainchillas 14 each -Flemlah Giants $5 each. PIN THIS TO YOUR LETTERHEAD 82 -page illustrated book, catalog and contract. "Yes, Henry, but how often does the man also copy of Fur Farming magnrine.telle bow to wave-meter?" twine skunk. mink. ns. etc.. for big profits, all for Inc. Addrers call to read the UTDOOR ENTERPRISE CO., Sax 73 Holm.. Park, Mimosrl -Wireless Magazine, London

www.americanradiohistory.com Radio News for April, 1928 1177 Dr. de Forest Talks on Radio as the socket -power units and the A.C. tubes are a little further perfected. (('mrtinued from par /e 1113) Mat. Gtatxsuu.teK:- electrify your set nuildi(leation and, particularly, better loud INlmt are your views out television, in vireo speakers. I do not consider any of the of the past experiments by Baird of Lon- c :s now on the market comic anywhere don, and by the research engineers of the the earyprae/ical near the perfect loud speaker. Cones in- American Telegraph & Telephone Corpora- variably favor some frequencies at the ex- tion? Do you believe television attach- Knapp and the cones, .eels rt near way pense Of others of while ments to radio matter of the over -emphasizing the bass, put a mask of f rehire? If so, how soon? "paper rustle" over the higher frequencies. Dn. nn Forms : I am quite naturally in- Although more expensive, more clumsy, and terested, and have inspected the work in demanding more space, and altogether less television which has been carried on in this artistic. there ore certain types of non- country, particularly that by the American metallic horn, now On the market which, Telegraph & Telephone Corporation. I with proper loud -speaker units, give far must pay the highest possible tribute to the better reproduction than ;my 18 -inch cone. ingenuity and patient research which has I strongly advocate a radio set built into made possible the system employed by Ow a large console cabinet with sufficient room) American Telegraph & Telephone Corpora- to take in One of the larger exponential tion. It is little less than a scientific mir- horns. I know of one or two such combina- acle. Nevertheless, I know nn- views on The Kit completely assembled with tions of radio and phonograph in one cabi- television have been somewhat disappointing metal cover in place. Operates on 7 being developed, on i net now though not yet to those who wish to believe that in the 105 -120 volts AC, 50 to 60 cycles. the market, which give incomparably better next few years every one can have a mov- sound reproduction than anything with ing- picture show at home, broadcast direct which the radio public is familiar. from his favorite theatre. Frankly, I can- Knapp A POWER HIT not foresee such a millennium) for the radio Ma. Gimxsn.tcic: Tubes, no fan. Until some radically new discovery No expensive short lived AC re- wiring, no annoying hum. I) . rte I'oresl''r you convinced That the has been made in physics, some new prin- troublesome present -dap alternating- current set is a Increase instead of decrease the efficiency ciple or operation of which we today have the Knapp step in the rip/ht direr!io?,I of your set, no waiting... "A" no clear conception, television apparatus Power gives you music instantly at the must continue to be extremely intricate, the. iw Foatsr.-As to the technical de- snap of a switch. delicate, requiring the constant and most velopments awaiting us in 1928, very rapid This absolutely dry "A" Power is not in careful attention of highly- skilled experts, . not progress has lawn uurde by a number of any way a battery combination and be and operated at very add your battery . it leading mnnufnclurcrs in the solving of the built great something to to is the most efficient "A" Battery Elimina- problem of applying raw A.C. to the fila- cost. Until such a new discovery, therefore, I think- we must limit our television ex- tor ever designed. It supplies unfailing ments of the tithes and several first -class set 201 -A or 6 pectations to an occasional demonstration "A" current to any using sets ore Ilaw an the market using these volt tubes, regardless of number. ruder the auspices Of one of the great tubes, thereby Iniug made cnfirely hule- few Magic Silence pendent of ": \," "It," and "C" batteries. electrical engineering and manufacturing corporations. Television in the popular So silent is Knapp "A" Power, that you There is nO question that the trend of the mind means radio broadcasts of distant can place a pair of head phones directly industry is eitirrly in this direction and and not be able to detect scenes as they transpire. across the output that, during the cnsuing twelve months, a hum. This is trade possible by the we will sec the storage battery eliminated, I have little patience with some of those efficient Knapp filter system, consisting of except for the cheaper cIass of sets. This whose moues are associated with the history 2 over sized chokes and 2 condensers of 1500 makes will be a development which every user of of this new development, who seem willing n» crofarads each. A new discovery the radio must heartily appreciate. The stor- to impose on the gullibility which the pub- these amazing capacities possible in lic evinces whenever word "Television" small space of 2x2x8 inches l age battery has from the start been a very the Dry serious nuisance in the home and will shortly is used. .\ few years ago it was impossible Absolutely There is not a drop of moisture in this absolutely dry he quite superfluous wherever electric cur- to get anyone to believe in wireless teleg- unit. 'l'he condensers are baked so tlmt not a drop of solid. rent, A.C. or 1).l'., is available. The better raphy, and later in time possibilities of the moisture remains. The unique, fully patented, how- full -wave rectifier is absolutely dry. No water ...no type of console radio with built -in speakers, wireless telephone. Of recent years, Reid . no alkali .. no tithes ... no electrolytic ones with ever, the progress in popular science has action. Nothing to get out of order. Nothing that particulnl' the higher -priced muds attention. phonograph combined, will be more and been so phttmm omal that general gull i t iii i ty, Hour or willingness to accept any prediction along Assemble in Hall an more in demand. And as prosperity be- The Knapp "A" Power Kit is so easily assembled. comes more widely di,tViluled, and particu- the lines of invention, takes the place of that within bait an hour after you receive it, you can the skepticism which formerly made the have it in operation. The parts seem LO fall in place, larly as the cduralive influence of radio No drilling and very little soldering. Everything works its insinnatke benefits, more and work of pioneers so difficult. supplied, even to tite screws, wire, drilled base -hoard and metal cover. It is so complete, that even a plug more will the radio public favor the more \ht. Gr :axsaaci: .Bearding to your is supplied so that a "B" Eliminator may be operate expensive and properly -designed amplifiers thoughts, /)oe(or, I presume what ,you mean from the same switch. We have never seen such simple instructions. and loud speakers. by a acto development in physics would be a television op/meatus without revolving Big Profits for Mn. Gu nxsut.tcrc:- parts, such as That we have at the present Set Builders ¡'or the next question, Dr. de Forest, the time? Our president, Mr. David W. new so- ealled "screen-arid" tubes make it Knapp, is offering the set Dn. us Fmusr: -Ses, I think that such a builders of America, for a possible to tise itrneh lex.v current than the limited time only, a money- development will eventually be made, but old -type tubes. Do you thin/,' multi-tube saving, profit -staking plan it will be the result of some discovery as which is unique in the annals sets with little butter¡/ consumption a pos- of radio. Send the coupon radical and as unexpected as was the in- sibility, and that battery- operated sets might today, before it is too late. vention of the X -ray by Roentgen; and not yet prevail in the fi,tire? until we have another Roentgen or Michel- Knapp Electric Corporation Port Chester. N. Y. Dn. nit Foiu:sr :- Notwithstanding the son who produces or makes a new discovery greater current economy which the double - as radical as time X -ray was at the time he Mil. DAVIT) W. KN APP, Pres. grid tubes permit, I do not think that multi - made it, may we bring into existence the Knapp Electric Corporation tube sets for battery consumption will ever television which we all would so gladly 312 Fox Island Rond, Port Chester, N. Y. again he welcome. popular. i think the day of gen- Send me complete information regarding the Knapp eral use of the storage battery and the dry MR. GERxsn,tex: -I think you are a little "A" Power Kit and your special discount to Set Builders. battery is rapidly drawing to an end. The too modest, Doctor, when you mention as great convenience and sense of satisfaction an example the X -ray. Why didn't you say Name in knowing that you are not dependent upon the vacuum) tribe? You are the one who in- Address a battery which may give out in the midst vented that unexpected wonder. Let me ask of n particularly- desired program, will out- you the next question. weigh any other considerations just as soon 1i'hat, to plover mind, while we are talking

www.americanradiohistory.com :178 Radio News for April, 1928

of vacuum tubes, is the ideal vacuum tube of the future? What should be its out- standing point? DR. DE FOREST:-I think the ideal vacuum tube of the future should operate without Here are the batteries, it should be small, ruggedly- built, 0e-00-lie absolutely free of all tube noises and non - uticrophonic. It goes without saying, that answers to all your receiver. it should be operated without overloading anti with absolute freedom of alternating- your questions current or direct- current noises. I think that such a vacuum tube will be produced within the next two or three years. MR. GERcSDStCI :-That is very interesting, Dr. de Forest. May I ask you, what are the latest de- velopments on your "Phonofilm ?" Has it been completely commercialized, and inhere, at the present, is it nto,et used.? DR. DE FoREsT Answering that question, it has not been commercialized completely, hut everything is being done to prove, to most of the motion -picture magnates and authorities in this country, that it is going to occupy a very important part in almost' all motion -picture programs in the future. Operating your A. C. Radio Set In this respect, the attitude of the men that with a worn or defective tube is control the industry has completely changed like running your car with a miss- within the last two years. I alight say that ing cylinder! great technical progress has been made dur- Replace the defectives with CeCo ing 1927 in perfecting talking motion pic- A. C. Tubes. They will work in tures, including the method using phono- There'll be no harness with any other unworn graph records, and the Phonofilin method tubes you have. of photographing sound -waves on the mar- Radio Trouble But you'll get better results, gin of the film. Both systems have been clearer tone, greater volume, longer amply demonstrated before the public in life if you CeCo -ize your receiver motion -picture theaters, so that it is now Wrinkles now! by putting a CeCo Tube in every fair to draw certain conclusions relative to socket. the practical and commercial possibilities of Isere are the solutions to Radio Your dealer will help you select the the two -the one exploited by Warner Questions of every conceivable correct types for your set. Ask him. Brothers as "Vitaphone," and the other by nature. the Phonofilm Company and by Fox under Have you a question to ask about the name of "Movietone." It is only fair Radio? -about this circuit, that to state at the outset that Movietone is a circuit - this method or that complete copy of Phonofilm, differing in no method of Amplification, Balanc- essential manner the method, ing, Regeneration, Transmission, from earlier Set Construction, Operation, but having been exploited commercially to Speaker Design, Control, Electri- a much greater degree. The practical ad fication, Accessory Installation, vantages of the Phonofilm method over that Antenna Possibilities -? of the synchronized phonograph in produc- Then keep this book of 1001 Radio ing, and also in reproduction, have been so Questions and Answers always dearly demonstrated to those who are fa- near at hand. miliar now with the actual manipulation of the two methods in studio and theater, as to 1001 R. I DiO QUESTIONS AND ANSWERS- wherever there is a Write for confirm beyond any question the correct- question or a doubt you are dcscriptirc circular ness of my prediction (made in 1919), that certain to find a solution here. the success of the talking picture would lie C. E. MFG. CO., Inc., Providence, R. I. eventually entirely with the method which These are the questions that the Largest E.rclusire Radio Tube Mfrs. in World. readers of Radio News have asked, photographs sounds on the film margin. are asking, and will ask -and now, OVER 3 MILLION TUBES IN USE With the Phonofilm method an entirely new with this book in your home, you art and technique had to be developed from can have them answered whenever the very beginning; whereas, with the you ask them. synchronized phonograph we had a highly - developed industry of the past thirty years 1001 RADIO QUESTIONS to fall back on. The first six years of AND ANSWERS Phonofilm pioneering resulted in solving the basic problems and demonstrating to any unbiased technician that the method 50c. was practical and could without question be ON ALL NEWSSTANDS eventually worked out to a point of perfec- tion equal to, or excelling, the phonograph If your dealer has none on hand art. Both the modern method of recording USE ONSINGLE DIALRAD CONTROL and reproducing from the phonograph and COUPON COMPLETELY SHIELDED from the GENUINE LICENSED CIRCUITS that of recording and reproducing Phonofilm an immeasurable debt to the EXPERIMENTER PUB. CO., Inc. RADIO[ CORPORATION OF AMERICA owe 230 Fifth Ave.. N. Y. C. send The set thaandthe talk of the radiotirade. Manufac- radio art, or more particularly to the art of Gentlemen: Kindly Immediately your tura under license grant insures highest quality: 1001 RADIO QUESTIONS AND ANSWERS all vacuum -tube amplification. Without the book. Enclosed Is 50e. ceta.aiÌ.ttesortthlóRtei dfeatures vfoundllumifinest dial. Very Selective and ¢ n suive. Gels long tir highly- advanced technique along this line ronce st tien with wonderful tone and volume.Ta- ble and console models in newest o49ea and designs. which broadcasting Name Yourself Day the demands of radio GonRad Ires liven paso any demand. have produced, Vitaphone or the Phonofilm day Free Street address and be satisfied. If you are not thee receivver tucompleteand the money wi:: be refunded. today in their present states of perfection would catalog and details of the GonRad Line of18_8 and our liberal an Day Free Trial Offer. be quite impossible. But taking full advan- city State CONSUMERS RADIO Dept. 152 4721 Lincoln Ave.v CHICAGO tage of what the radio broadcasting art has

www.americanradiohistory.com Radio New's for April, 1928 1179 produced along these lines, there still re- The chief remaining problems in the talk- main very difficult and intricate problems in ing- picture art lie, not in the theater or i'honolilmm; particularly as regards the light - engineering laboratory, but in the motion - recording, sound- photographing means; and picture studio. There scenario writers, pro- the successful taking off of sound from the ducers, artists and cameramen must gradu- photographic record on the film. And in ally acquire working knowledge of the new between lie many problems in photography, art and how to take full artistic advantages exposure, development, printing, and pro- of the countless and itirmeasurably rich pos- tecting the sound record. sibilities which this new art lias now brought Great progress has been made in the per- for entertainment and cultural La u forth, the fecting of the "photion," or gas -tilled lamp, [uplift of the motion -picture public. which is placed in the camera and which, Mn. GER\snAcll:- iIy final question: SPEAK R, when connected to the output of the On what particular new thing are you vacuum-tube amplifier, reproduces perfectly working now, and can you tell sis something in light variations the electrical values im- about it? PER ION pressed upon its terminals. The 'Motion Dn. iw FoR1:sT: -I am working exclusively tithe, which I first conceived in 1918 and on Phonofilm and allied problems at the patented in 1923, has thus far proved its present time. Among these are improved frorin a distinct superiority over other methods of audio-frequency amplifiers and loud- speaker telephonic light control, such as the vibrat- devices which can be used in connection ing mirror and the `light- valve." (The with either Phonofilm or with radio, or the latter is a type of bi -filar Einthoven string electric phonograph. galvanometer, acting as a shutter to "valve" the light from a fixed source). While the NO "TUBES" - NO "B" BAT- portion is not vet fully perfected, its re- TERIES - NO COSTLY production, in light fluctuations, of tele- phonic currents impressed upon it is Só What Constitutes Tone "ELIMINATORS" nearly perfect, throughout the useful range WITH of audio frequencies, as to justify our faith Quality ? in its continued supremacy in the field of THE SKINDERVIKEN sound photography. Its simplicity, compact- (Continued from page 1135) ness, lightness of weight, and ruggedness, as portion of the vibrator near B. The lower - TRANSMITTER compared with that of the vibrating mirror pitched waves produced at the rear must UNIT and light-valve, argue powerfully for its travel farther before emergence than the Simple mlcropnone unit provides a most effec- continued use in preference to the other higher-pitched waves generated near B; in tive and inexpensive way to satisfactory speaker I ypcs. operation. Easy to build and operate circuit. both cases the necessary conditions for Everybody can do this now with Particularly do the above advantages hold amplification. It should be noticed that the a Skinderviken Transmitter Unit. for portable Phonofilmi or \Iovietone equip- The unit is fastened to the dia- vibrator board, as a' sound amplifier, func- phragm of the speaker unit. It will ment, where a light, easily -portable camera, tions much as does the disc of a fixed-edge act as a "microphonic relay." Every to be quickly from a truck and set time an incoming signal actuates carried cone. the diaphragm, the electrical resist- up at a moment's notice for recording "It may be seen that the horn described ance of the microphone unit will be swiftly- passing topical events, is absolutely varied correspondingly and the cur- is not a simple air -volume resonator, but rent front the battery, in series essential. And the success of the audible that it is a combination in a single instru- with it and the loud- speaker, will fluctuate accordingly. topical is so abundantly Thus the problem of securing sufficient power weekly already ment of a series of air resonators, a reflex to actuate the Loud -Speaker is simply and adequately demonstrated as to prove that, in the fu- horn, a straight horn, a curved horn, a re- solved. this will become more and The results front this very novel and simple unit ture, feature entrant horn, and a resonating diaphragm will astound you. more essential in every motion -picture pro- or sounding board; use The expense of this hookup is trifling compared and that it makes to elaborate tube circuits that give no greater actuation gram. Much progress has been made also of both multiple and cross resonance, all in of the speaker. in the design of compact portable ampli- the effort to secure as nearly as possible Besicles this there are many other valuable uses in of outdoor news Radio Circuits for this marvelous little unit. Every fiers for such recording uniform tone amplification." builder of Radio sets should have a few on hand. events. The difficulties in securing perfect motion LISTENING THROUGH WALLS of the film past the light source in the This Unit makes a highly sensitive detectaphone, the real thing-you listen through walls with ease. camera have been eliminated during the past BREAKING INTO GOOD COMPANY Plenty of fun and real detective work too. year; so that now it is possible to secure It is evident that Walter Damrosch, con- CONDUCTING SOUND THROUGH as perfect film motion with a cheap portable ductor emeritus of the New York Symphony WATER be projection machine as can obtained with Orchestra, derives great enjoyment from Make yourself a miniature submarine signalling the finest phonograph turntable. his fan mail. He told with particular zest apparatus like those used during the war. Simple For use in the projection room of the circuit with this microphone unit gives splendid results. of a South Dakota listener-a plainsman - nation- picture theater highly improved writing to say that when Mr. Damrosch was 12 -PAGE INSTRUCTION BOOKLET amplifiers with sound "fade -in" and "fade- broadcasting the containing suggestions and diagrams for innumerable "Pilgrim's Chorus" from uses mailed with each t. out" devices have been largely perfected. Totnthaifser that he grabbed up "his old '1'hc Phonofilm amplifier for the theater has cello" and ,joined in. been made very compact and fool -proof, re- "I did that," the plainsman confided, "so We Pay $5.00 in Cash quiring practically no skill on the part of that I could say I once played with Walter the motion- picture operator for its proper for every new use developed for this unit Damrosch and the New York Symphony and accepted and published by us. manipulation. Back of the screen has seen Orchestra." possibly the most striking advances of any in this art during the past year. New loud i speakers of entirely novel design, permit- SEND NO MONEY LET THE BUYER BEWARE ting a naturalness of reproduction which Order as many as you want -use the coupon below is almost uncanny, have been worked out. ALTHOUGH European listeners When the postman delivers your order you merely are held pay him 95e plus a few cents postage. If you order A new form of screen, transparent to sound strictly to payment of a fee for the two units you pay him only $1.75, plus postage. and possessing the necessary optical prop- privilege of owning receiving sets, in Ba- erty to throw a brilliant picture, has been varia they are allowed a week's free trial of PRESS GUILD. INC. R-4-28 found; so that the sound no longer seems a set purchased on approval, without taking 16 -18-R -East 30th St., New York, N. Y. Please mail me at once Skinderviken to emanate from one side or the other of out a license. In England, however, the Transmitter Units, for which I will pay the postman the screen, but directly from the mouth of radio magazines complain, pic. plus postage, or 81.75 plus postage if I order a number of pub- two units. the speaker, wherever he may be in the lic functionaries seem to be of the opinion picture. 1928 will see these various improve- that it is an offense against the. law to pur- Name ments, which I have described, exploited chase a radio set without having a license Address and demonstrated to the public in many in advance. This places radio apparatus hundreds of theaters scattered throughout somewhat in the category of revolvers and City Sta te the country. narcotics.

www.americanradiohistory.com I Radio \'cws for April, 1928 Broadcasting in Foreign Converts Tongues T N the September, 1927, issue of RAUto An Efficient 1 NEWS, one of our contributors, Charles I Any Set to C Mt gee Adams, discussed the effect of radio broadcasting on American speech, and com- mented that foreign -language broadcasts in ONE DiIAI. this country, save for a few elementary les- sons, seemed unknown. He was corrected by the sponsors of Ger- RECEIVER man broadcasting over station WIBO, Chi- cago, who had put on regular cultural pro- grams on Sundays for those of German a reality speech; but since that time "Mike" seems to have acquired the gift of tongues. Sta- tion WCDA, New York, devotes a consider- able portion of its time to the exploitation of the melodious Italian language; and now WMBI, owned by the Moody Bible Insti- tute of Chicago, has undertaken Scandi- navian services on Saturday evenings and Tuesday afternoons, German services on Thursday afternoons, and Yiddish services The KARAS on Friday evenings. The European listener may acquire a A- C- radio familiarity with practically every lan- FORMER guage of the Continent, as he sweeps his battery troubles and Type 12 supplies dials from Moscow, Motala and Angora to ENDbring your set up-to-date un to 8 -220, 2- perhaps the 227. and 2 -171 Madrid, Paris, and Cork; with this new Karas achieve- tubes. ment! Delivers correct volt- American will have an opportunity to culti- age to the new AC Tubes 226 vate the linguistic faculty hitherto so neg- and 227. Does not permit ex- cessive voltage and current 75 lected in the United States. fluctuations, insuring long life to your AC Tubes. Needs no separate device for center tap. Has plug -in connection for 11 Eliminator and loop of wire Possibility of Receiving for connection to panel switch. LIST PRICE Write for details to Europe THE PERIDYNE, due to the KARAS ELECTRIC COMPANY HAWING the advantage of the time dif- new principle on which its 4038C-North Rockwell St. Chicago, Ill. ference, European fans hear American stations in the small hours, as Yankees construction is based, assures hear the Pacific Coast. Recent reports in- positive true Interstage Reson- Announcing the dicate that on January 16 unusually good ance, and thus the perfect one- reception of American stations, even as far dial receiver has become a TABLE- TYPE west as Oakland, was reported throughout reality. England. Distance, tone, remarkable per- While the distance from the eastern formance under all circum- CLAROSTAT United States to Europe is not so great as that from California to Japan, the Ameri- stances- these are but a few 'CST the thin; for the set! 51ierometric resistance In of the remarkable accomplish- convenient at'flsory form. No need for extensive can is handicapped by the fact that mid- changes. No need for tools. No need spending time and night in England, or 1:00 a. ni. in Ger- ments which can be had with effort. Just connect In circuit by means of handy connection cords and connection block, and you have micrometric many, is only seven o'clock in the evening in the Peridyne. resistance at work Improving results. for volume contra your Ideal New York. For that reason transatlantic Note the schematic symbol that Finished in statuary bronze and nickel. Bakelite knob. Felt bottom. Two connection cools and tip connection reception, though, highly interesting, has had to be specially designed to block. Ample resistance range. Sumrlent current- handling never been many American capacity. Resistance range In several turn, of knob. Bolds practicable for designate the Peridyne char- resistance set ling. Foolproof. Durable. A de» lane claw - listeners; especially as hitherto the highest slat, In a new dress. And all for $2.50, acter. No other symbol of this Wit American Mechanical Lab., Inc. powered stations of Europe have been out is 285-7 N. Sixth St., Brooklyn, N. Y. of the 200 -600 -meter band, requiring spe- arrangement provided in Ask your dealer to show you _ radio practice. this and other Clarostat., cial coils in receivers tuned to them. And ask him for booklet However, (hiring the there has 5 Full "Radio Ií1 hotel te." or past year -sized blueprints and a secure direct been a great increase in the number of from us. 16 -page instruction book. super -power medium -wave stations in Eu- Send today for the complete rope; and it is quite possible that in good locations, free of other interference, some blueprints and constructional of these might be received early in the eve- data for the Peridyne -only 50c. ning in. parts of the United States. Build this set and prove to Poland has opened a 10- kilowatt station yourself its remarkable features Your Next `B" at Katowice, operating on 422 meters. The and high efficiency. Power Supply short -wave transmitter of Daventry, Eng- Had Better "B" the land, 5613, has been increased to 30 kilo- INC. watts, it is said; though unfortunately its CONSRAD CO., NATIONAL BETTER "B" waive is that of WEAF, 491 meters. Milan, 230 Fifth Avenue New York City NATIONAL CO., INC. MALDEN, MASS. Italy, has now notch higher -powered equip- ment on 545 meters. Hungary has a "60- CONSRAD COMPANY, INC. SPECIAL PRICES kilowatt" (25 -kw. input) at Czcpcl in the 230 Fifth Ave., New York City Itulld hag Scot tbworld' »Record Ten. Nine -ln -laine and Tyrman Danube, near Budapest. And headlines an- Gentlemen: "70" and all other kits. Rend for literature. Dept. N. Enclosed and 50e., for which kindly send me a NORTH SHORE RADIO LABORATORIES nounce that Zeesen, in Germany, is to he of complete set of blueprints and full constructional ASSOC IATES I. R. E., A. A. A. S. data for the Peridyne. (902 North Clark Street Chicago, M. higher power than the 100 -kilowatt trans- FORMICA KIT PANELS mitter at Schenectady (something to be re- Name Drilled and decorated for leading kit sets are :minable through garded with a grain of salt), and that Landing Jobbers everywhere. going this bet- Address THE FORMICA INSULATION COMPANY "Radio-Paris" contemplates =614 Srping Grove Avenue, Cincinnati, Ohio ter. with a 150 -kilowatt input. City elate

www.americanradiohistory.com Radio NON'S for April, 192S 1181 What the Federal Radio Commission Needs

1275 Nelson Avenue Here's what this new device will do: The Bronx, New York City. It will automatically stop any broadcast station from broadcasting, at the same time Editor, RADIO NEws: causing that same station to broadcast a This letter should interest you, because program sent through my invention, but it has to do with a great invention which on the carrier wave of that station. should revolutionize the radio industry, both It will be impossible for any one to de- commercially and scientifically. tect who has stopped the programs of the Ever since radio became popular, I began station, and unless that station shuts off to tinker and experiment with different its power, I will be able to send my- own kinds of hook -ups and devices for the im- program on the station's carrier wave. I provement of radio. It got me like a cross- have done it, and it has proved entirely word puzzle. Once I began, I just had to satisfactory. finish. I spent almost as much money on It took me almost four years to perfect triple bromides as I did for radio material. this device. Hard work and money bor- Mozart- Radioceive Edison paid large dividends last year be- rowed from friends and relatives arc re- cause of ate; because I stayed up every sponsible for its success. Speakers and Speaker Units night until early morn, until night, every Two weeks ago I gave it a practical test FOR SEASON 1928 -9 my eyes shut involuntarily. at a radio broadcast station, located in But my efforts have not been in vain. New Jersey. TANS who know that the Loud Speaker Unit is the very heart I have finally succeeded in inventing a My device had to be delivered on a truck of any Radio, are demanding device that will undoubtedly prove the big- and had to remain on the truck as the ma- better and better performance, gest and most amazing radio feature since chine, or J'icortraph as I call it, weighs hence the reason for the Radio- Marconi sent the first message through the about one thousand pounds. The l'icograph ceive Twin Balanced Armature, ether. is portable, especially so made on account far outselling all others in this 11 market. ÌI My invention has been tried out in a of its necessity of being moved from place practical way, and those few who witnessed to place. Here indeed is true Push -Pull ÌI Tone Reproduction a fraction of ÌI the exhibition marvelled at its wonders. at first The unchinc consists of numerous coils, the cost it can be obtained in any 1 You will marvel too when I describe what water jackets, water coolers, heavy cables, other way, and with the very mini- II this new invention can do. Iicntentber, I dry- and wet -cell batteries, tubes, dials, mum of current consumption. and 11 have tried it out, and it worked. switches, and other accessories especially- voltages ranging all the way from 90 to 400. ÌI And for those who want a good cone unit at a lower figure, we offer our single balanced armature, which will outperform most others II selling at twice its price. Or in a complete speaker, our I"I Mozart 26-in. Wall -Cone (not a II kit) and Drum Type with these II units, are guaranteed on a money- II back basis to excell in appearance II and performance all others in Iti their class. 15 Single Unit, 5 ft. cord (I I50 ohms) $1.00 Twin Unit. 10 ft. cord (2000 ohms) 6.00 ly 26-in. Wall Cone Speaker, Single Unit 8.00 26-in. Wall Cone Speaker. Twin Unit 10.00 1ti Drum Type Speaker. Twin Unit 15.00 THE FERGUS CO. Iti 239 It ELIZABETH NEWARK, AVENUE N. J.

TRANSMITTING APPARATUS A Complete Stock at "Chi -Rad" In addition to our regular broadcast apparatus we carry a very good stoc:c of transformers, chokes, grid leaks, high test condensers, etc., for trans- mitting purposes. NEW SHORT -WAVE COILS Specially built by "Chi.Rad." Write for descriptive bulletin and catalog. Dealers and set-builders please use business letterhead when writing for discounts. Chicago Radio Apparatus Co. "The shrill, whistling sound ceased, and all that was heard was the carrier ware; a 415 S. Dearborn St., Dept. RN, Chicago carnal .eimilar to the one caused when steam escapes from a radiator."

www.americanradiohistory.com 1152 Radio News for April, 1928

designed for this particular device. They are too numerous to mention here. I will now give you a description of what occurred at the New Jersey broadcast sta- tion when I made my first practical test. DIESEL 81 OIL The truck was placed about a hundred yards from the transmitter. The station began to broadcast a program of dance music played by a fourteen -piece orchestra. ENGINEERING The station used a frequency of about 1010 kilocycles. (I do not wish to mention the name or exact frequency of the station at the present titile.) HAND BOOK l'he band got well on its way into the middle of its first selection, when I began (Rosbloom) to move a lever, slowly, to the point on a dial on the Vicograph where appeared the , figures 1010. Through my receiver, which :wYHI3;:4' j = was part of the outfit, I could hear a whist- ling, shrill noise, becoming fainter and L`.34 fainter, until the pointer on the dial was , ÈAGÍ .EÉRI ,i:í directly over 1010, the corresponding num- ber of the transmitter's frequency. The igittfr.TSi-:RO : LOÚ'T shrill, whistling sound ceased, and all that s:i'-4, ,fY.»%i .;;?.t:.::i:':'", ñi%_ was heard was the carrier wave; a sound é +,t similar to the one caused when steam es- v+".'..aLsr' ëi'S7 . al.'rl¡%: >.t; b }'+.¡ capes from a radiator. . é That was wonder number one. (iéñiiflñiv*'ï ,M{.1.T ;ittq...is:fy¡.. y:Srl'.: aware of what was going on. I was doing L!;'-,. -...a ¡+:,:: all this with their permission, and they were '..1"l- truly amazed, bewildered, astonished, and I1á: i''°iéityii aj.-: Id--ní_izi puzzled. 'l'he six men, all radio engineers, stood there, open mouthed, open eyed. They Fourth Enlarged Edition were stunned. Aotearr.óui/d I did not stop the experiment right there. A remarkable book of great- I went on. your own, est value to all engineers, Included in the outfit was a shall portable talking machine. This machine was mounted mechanics, and others in- next to a microphone of my own design. I terested in Diesel engines turned on the phonograph, and a record LOUDSPEAKER, for land, marine, locomotive, was played. THIS a automobile, and aircraft use. I began to move on an- book, complete history of another pointer radio acoustics, has been compiled Over 300 tables, hundreds of other dial. As soon as the pointer was by Clyde J. Fitch and many other formulae, profusely illus- over the figures 1010 of the second dial, the eminent authorities on loud -speaker trated with color and plain receiver brought forth music being played construction. The data thus assem- views. Courses of instruc- by the phonograph. bled is now ready to be presented That was wonder number two. to you in the most comprehensive tion on all leading types. . One of the men present skeptically asked manner yet achieved. nie if it weren't possible that the Vicograph 830 pages. Size 5 x 7 inches. 'Way back in the days of "canned Bound in flexible, semi -flex- also consisted of a transmitter which broad- music," those hectic days when dis- ible and stiff covers of very cast the phonograph music on its own wave- tance was all -engrossing` to the radio attractive imitation leather length, and picked up by the receiver. enthusiast, and up to the present with reinforced back. I suggested that we ride over about a time when true tone reproduction mile from where the truck and device stood, is the objective of every radio fan - and listen to some other radio receiver. through every phase of this develop - Price $5.00 Prepaid We got into a car and drove off to a ment-to each milestone of this progress, Chinese restaurant. There we were per- this little book will take you. Order Direct from Book mitted to tune in on 1010 kilocycles, and Department Every type of loud speaker -the sure enough, we heard the song being played Exponential Horn - the Cone the on the phonograph. My assistant remained, Piezo Electric Loudspeaker -Power- EXPERIMENTER PUB. CO. of course, to continue to play the record as Speakers, and Roll Type Speakers, and soon as it ended. many more, fully explained. Complete 230 Fifth Avenue, New York One of the men even called up the en- constructional data, diagrams, etc., assure positive results for gineer at time broadcast station to if the experi- learn menting fan. the band was playing. He replied in the BUILD THE NEW SHIELDED affirmative, and also gave out the informa- 52 pages, 6 x 9 in., illustrated tion that an entirely different program was being emitted from the transmitter's radio 25 Cts. Rmm arlund than the one being played by the band. He On all newsstands -if dealer has nono too was puzzled. write direct Assured that my invention was perfect, Send 25c for Construction Book Hammarlund - Roberts, 1162 Broadway, Dept. C, New York we all went back to the truck. Then I re- CONSRAI CO., INC. adjusted the dials, and once more the sta- 230 Fifth Ave., New York City tion's program was heard. However, I Gentlemen: Kindly send me a copy of your nteresting w ent a step further. new book, mow to Build Modern Loudspeakers," We tuned into a powerful New York for which I am enclosing 25c. WRITE broadcast station. An opera was going on. Page Name For Our 32 I moved the pointer to that station's cor- Radio Instrument Catalog responding wavelength. The music ceased. Address No. 15C' Not only did it cease coming through my Ctty State JEWELL ELECTRICAL INSTRUMENT CO. when we 1650 Walnut St. -Chicago receiver, but inquired whether the program was coming over the New Jersey

www.americanradiohistory.com Radio News for April, 1928 1183

transmitter's radio receiver, the operator told us no. \Cc even tried out the receivers of some nearby dwellers, bitt there was no program heard. Only a carrier wave. I I Some of the radio listeners thought their sets had gone wrong, or that an SOS was Icing relayed, or that the station had soine technical trouble. Ilut we let them know that we were cluing this and that everything or improved would he Al right in :t few minutes. \nd everything was all right in a few musical performance minutes. 1 I tried the experiment on at least thirty stations, both nearby and distant, with the same results. \ \' even phoned several of .- the local ones asking if they had any diffi- a culty a few minutes :Igo, and they all in- E formed its yes. TWO told us that they had 0 ni:my phone calls advising them that their progr:uus were discontinued, but that they ors.- could not understand the reason. They were J "_.. e puzzled. R I wasn't. The other lien and I went back to the É ,' transmitter, then to Newark, to the studio. gg There 1 was introduced to the real owners of the station. Z+ - 3 Soon, L. several other prosperous looking E men joined its. 0 The engineers explained the invention to 7 the newcomers and for their benefit, I event E through the experiments again. They were anaared like the first Ones. 9 3 Iletbre lone, we began to talk about the E ArtioRDARS ON commercial value of my amazing invention, E E e E and soon an offer was made me. I refused e any offer. I told them so. But 9. . ., they in- . sisted that T sell the invention. Of course, 210 Power Amplifier , it was indented, and I had fifteen claims on various patents. and Plate Supply They took the initiative and offered nae ít:.511,0110. I merely sat back and took an- I other puff on my Lucky. 9 Easy to build - Simple to install - Economical "Well, gentlemen," said, I "if I nin going 9 to operate -Quiet in performance to sell, I aauldn't consider anything less E than a million for the I'ieofraph." GULL rich tonal reproduction with a generous supply of At that remark, several of the gentlemen 1 power for the heavier tones. You can bring your receiver got up and went into a conference in one up to these present standards of reception by building this of the corners of the spacious room. In a Thordarson 210 Power Amplifier and B Supply. E fete minutes they returned to the table. One of the men stood up and said, "Sir, Easy to build. Every effort has been made to make assembly we have talked the matter over carefully, as simple as possible. The metal baseboard is equipped with and upon careful consideration, we hays all sockets and binding posts mounted. All necessary screws, E decided to pay you the amount asked for- simple E a million dollars." nuts and hook -up wire are furnished complete; pictorial Of course, I slid not act surprised be- E diagrams are supplied. You can assemble this unit in an hour. E cause I expected that amount. I knew é Simple to install. No changes in receiver wiring are necessary. that someone would pan it, and I consid- This amplifier can be attached to set in a moment. ered this party of men fortunate in having obt: sl such a wonderful device, a device 1 Economical to- operate. Highly efficient and cool in operation. that will revolutionize radio. Consumes less current than a common go watt lamp. One of the party took a small check hook E Qiliet in performance. The reliability of Thordarson engineer - from his pocket, and with a quick stroke ing assures you of unquestionable performance and quietness of his fountain pen, wrote out a cheek for one million dollars. E in operation. T took the check, shook hands with all E FOR SALE AT ALL GOOD PARTS DEALERS the men around our -and then I woke up! I VICTOR W. COIIEN. Write for this free booklet

DEPTH OF DEBILITY 1 THE THORDARSON ELECTRIC MFG. CO. MRS. WILT. 1)oot.rrrt.t:: "My husband's so 500 W. Huron St., Chicago lazy he won't do nothin' but set to home and GENTLEMEN: Please send me, free of charge, your booklet describing your listen to the radio." 210 power amplifier on the metal baseboard. Mus. U. S. T.zss: "I-Iuh! My old man's so churned lazy he won't listen in unless I'm Name ______home to turn the dials for hint." E Street and Ne. TO RILE 'EM ENOUGH et It is said that both Dempsey and Tunney - Town State want to fight in England. We're not sur- xrc prised, considering the dreadful radio pic- tures of the pugilists published in this coun- try.- London. Opinion.

www.americanradiohistory.com 1184 Radio News for April, 1928 What's New in Radio (Continued from gurte 1119)

the current flows through the battery in the correct direction. To do this, screw the connecting plug into the socket and turn on the switch; if the connections are correct the ammeter should read "charge." If the meter reads "discharge," remove the cap of the connecting plug (leaving the body in the lamp socket) turn the cap o:ie-half turn (180 °) and replace the cap in the body. The meter should now. read "charge," in- dicating that the circuit connections are correct.

Center -Tapped Resistor For Some of the amazing stories you will find in this issue: A. C. Tubes THE MOON OF DOOM Experimenters who are rewiring their old By Earl L. Bell receivers for use with the new A.C. tubes and those who are building alternating-cur- THE ATOMIC RIDDLE rent- operated receivers will find great con- By Edward Shears venience in the use of a new type of center - WHEN THE SLEEPER tapped fixed resistor. The units are avail- WAKES able in several resistance values, and so By H. G. Wells designed that they may be fastened directly to the filament terminals of any tube socket. THE PUZZLE DUEL One connected in this way provides an ac- By Miles J. Breuer, M.D. and others

STORIES of other worlds -of Don't miss this amazing quarterly other people- stories of future edition of AMAZING STORIES. 150 pages -large magazine size, 9x12 in. ages and future happenings -each At all newsdealers one a gem of the imagination - Amazing So Cents truly Stories. or write direct to the DETAIL. OF WINDING EXPERIMENTER PUB. CO. Tales never before conceived- 230 Fifth Avenue New York City dreamlike- carrying you far from this world to new places -mystical EXPERIMENTER PUBLISHING CO., Drawing shows details of new "6"' tyfc ccn ter 230 Fifth Avenue, New York City lagged resistor unit. It consists of two units beings -weird happenings. Ad- of tine resistance sire wound on an asbestos venture mystery science Gentlemen: core. - -a me - Kindly send copy AMAZING one of

touch of each combined to make STORIES QUARTERLY. - Enclosed is 50c one of the most remarkable vol- Name curate electrical center for grid- return leads. umes of the age. Tales by the The illustration on this page shows the most famous writers. Address mechanical construction of the resistor unit. City State It consists of two wires fastened together at one end and forming a "V" shape, with soldering lugs attached to their other ends H E for making connections. Each wire is of identical construction and resistance, and consists of a core of asbestos cord on which YouIT'S Will ,E has been wound a single layer of very fine resistance wire. The resistance wire is space - Like It-and Profit! wound on the asbestos core, in order to --_ - give the unit a total resistance equal to that of the wire used; and each resistor unit RLD'S GREÁ1'EST is covered with spaghetti tubing for insulat- ing purposes. Now Free -Send for your copy today! The resistance units described may be The best in Radio -at a big used in many different parts of A.C. re- saving -all under one roof. You don't need to look else- ceivers. They are available in eight sizes, New kits featured Complete stock carried. where. Contains all the in- ranging in resistance from 10 to 200 ohms, include: Aero-Bo. Prompt, efficient, formation you need. dine-Camfield-Cit' dependable service, for connection directly across circuits hav- icons -H -F -L - Infradvne - Hares - always. ing maximum working voltages of from 3.5 Melo- Meald- Scott's -Silver Marshall - volts to 17 volts. For use in the filament James -Tyrman Established -etc.St. 2918 circuit of 226- or 227 -type tubes a 10 -ohm unit be used, in that of a 171 -type CO. should TELEPHONE MAINTENANCE 30 -ohm unit; and with a 210 - 123 South Wells Street Dee ?. 71 Chicago, Illinois tube a 20- or or 280 -type tube a 0. -ohm unit is required. For circuits having higher voltages, the re-

www.americanradiohistory.com Radio TOWS for April, 1928 sistancc of the units employed should be increased in proportion. Course .1 Two New Resisters Answer Of Power -Unit Needs You know that this is not a modification of existing obsolete circuits. Two new resistance [nits, which answer the requirements of the builders of "B" socket -power units, have recently been put on the market; both will be found illustrated in these cohnnns. One is an adjustable (tapped) resistor, designed especially for providing a voltage drop to be used in biasing the grids of amplifier tubes; and the second is a rheostat potentiometer in differ- ent values, for which there are nnunv ions in the voltage- dividing circuits of eInecr (nits.

Rear view of Nob resistance rheostat .dross method of mak- ing adjust isle,,! with cent a arta. The units arre t'onii, bic iii le steps, and TUNING UNIT may be eon- veiled as either Being one-third of the circuit. This is-in conjunction with the potentiometers or original and new audio frequency and radio frequency units. rheostats. Will have the ideal radio receiving 'circuit (that will -give you - I. Perfect quality of reproduction 2. Absolute selectivity Both the tapped resistor and the rheostat 3. Tremendous volume 4. Unlimited'range are made by winding a special wire whose 5. Stability ofbperation resistance changes little with the heat, on a 6. Simplicity in tuning tube or base which is very heat -resistant, 7. Elimination of undesirable interference and coating the entire surface of the unit with the with a glass -like enamel. 'l'he enamel is applied by a method which is largely respon- SUPER-HILODYNE sible for the long life and permanent ac- Start Now and Prepare for the Demand We Are Creating curacy of units of this type; it covers the A new basic circuit employing nine tubes. World's latest -most acclaimed circuit -the SUPER -HILODYNE- radically new -much in demand -a sure money -maker for custom set builders.

The high -resistance rhe- ostat -potentiometer is POTTER PRODUCTS CORPORATION, Wanted Sesioned for one.hole moulding, und is ad- 15 -17 W. 18th St., New York, N. Y. we want direct factory repre- justed by a steall knob sentatives in all territories. located on the Write for details and front of Gentlemen: Please send nie immedknely full our unus- the panel. ual moneymaking proposition. details of your plan to help me make blgproats. 1 understand this does not nblbmte me in anyway wnalever, POTTER

I PRODUCTS CORP. entire surface of the resistor luui,in a firing Name 1 5-1 7 W. 18th Street process, is intimately- bonded with the sur- face of the resistatnce wire. The heat de- New York City veloped under the load, when the resistor is Address used, is in.slanth transmitted to the enamel and from the enamel to the air. heating and Chi' ..State cooling do not affect either the wire, the enamel, the refractory tube or base; as they all expand and contract alike. Also, the total resistance of the unit remains practically ELECTROMAGNETIC constant, regardless of the temperature. EROVOX POWER CONE UNIT Therefore, these units are excellently suited Operates on "A" battery cur- to the requirements of the radio power PTROIISI RESISTANCES rent. For all size roar speakers. will carry more current Enormous volume - :unazing units. without undue heating. Ìávquality. Sent C.0.1). The tapped fixed resistor has a total re- Ask your dealer or write postman 512.50. 10 -dav us for information. 70 Washington St.. money-baek guarantee. Ap- sistance of 375 ohms and is capable of dis- Brooklyn. N. Y. proved by Radio News Labor- sipating 12 watts. is equipped three atories. Designed by Clyde It with J. Fitch. taps and the arrangement is such that it is FANSPEAKER RADIO CO. possible to obtain 15 different resistance 74 Dey Street New York City DEALERS The ELECTRIC Radio See page 1176 Freshman DEALERS This tapped resistor may be used to obtain RADIO PERSONAL EQUAPHASE grid bias for potter tubes. when n .c»el :el -parer NEWS nuit is raser!. EDITION at All Authorized Dealers

www.americanradiohistory.com 1186 Radio News for April, 1928

values between 25 and :375 ohms. The unit is inches II c Q four long, approximately %-inch in O h Pf diameter, and provided with live soldering , Q . lugs for terminals. It will pass a current of j a Q 300 milliamperes and may be used in any So ,(s a QO CF I Q "B" socket -power unit without danger of c ï 4a 11111 burning out. is especially intended for ` I,P ` It ' P 'I1, ,i , ACt` \ use in circuits where the entire plate and i Q s Sa shunt- resistor load of the socket -power unit °` O P passes through the grid -bias -voltage resistor. 'l'he rheostat illustrated is made in thir- C,, N6 i D ( teen different values, ranging in resistance "'4 SpringEd,üen..._ F,l,yCe from 1 to 50,000 ohms. Each type is of c)-77; TuQR scoúr 4 Radio Listeners RQTE r+NE!ÑNE identical construction, and is capable of GuideánaCáll Book//':-4\-C dissipating 20 watts when mounted inside :I::: a cabinet or 25 watts when exposed to the air. The unit is provided with 16 steps, il'U¡. and its slider is adjusted with a bakelite knob; three terminals are provided, so that GìiÌ it may be connected as a potentiometer if D D desired. ß Cll u®®K i. Radio in Italy WHILE in America, we are told, it is up to the radio manufacturers to help out the broadcasters, in Italy the broad- There are the circuits to bui/d casters are anxious to promote the sale of FULL DATA. radio apparatus. This is because every new CONSTRUCTIONAL owner of a radio set, no matter how small, pays a license fee for the support of broad- Follow the trend of ra- these valuable books in casting. Accordingly, the Italian Broad- homes at all times. casting Co. ( Unione Radiofonica Italiana) dio - read the RADIO their has announced a prize of 40,000 lire (about LISTENERS' GUIDE and Besides the construc- $2,100) for the best new set design, pre- sented by an Italian manufacturer, of a set CALL BOOK. Full con- tional data there is a capable of bringing in all the Italian sta- tions on the loud speaker, as well as adapted structional data for the complete and up -to -date to mass production. A quarter of this sun will be awarded as a prize for the best above circuits, also for list of all radio stations home-built set, and an exposition of the en- many others. The RA- -their owners; call let- tries will be held. The company has been reorganized as the "E.I.A.R.," with a capi- DIO LISTENERS' GUIDE ters, wave length and tal increase to ;420,000. The possession of radio receiving sets, and CALL BOOK is the power ( watts) , also their even for broadcast listening, has been pro- hibited in several districts, such as the cities accepted chronicle of the locations. of Fiunte and Zara, near the Jugoslavian latest developments of frontier. This is an extension of the former No home is complete forbidden district, and is ruade for military the RADIO WORLD. and political reasons. :\ military as well without this accurate as civil permit must be obtained for an ex- guide. ception from this rule. In addition, a group Learn how to improve of patents obtained by Manrico Compare for radio inventions have been "expropri- your set by simple little The RADIO LISTENERS' ated" by the Italian government for pur- poses of national defense. They include adjustments and changes. GUIDE and CALL BOOK combination telegraphic instruments for radio or land-line use, which may be used Every radio fan or lay- is revised and brought up with a forms of typewriter.-E. Z. man should have one of to date quarterly.

Over 200 pages, fully Price Care of Electrolytes Now! illustrated Only I\ order to obtain long life and satis- Mail This If your dealer cannot supply you factory service from rectifiers and con- order direct densers of the electrolytic type it is essen- Coupon 50c. tial that nothing but pure distilled water be On all newsstands added to the electrolyte. This rule is just as essential in the operation of electrolytic CONSRAD COMPANY, INC. cells as in the case of storage batteries; for, 230 Fifth Avenue, New York City, N. Y. if city water from the pipes in the house Gentlemen: Enclosed find 50e., for which send me a copy of the latest issue of RADIO is used, the mineral contents may cause a LISTENERS' CUIDE AND CALL BOOK. chemical action which will destroy the ef- ficiency of the unit. If the electrolyte of a cell is evaporating too rapidly, it is possible to correct this by adding a small quantity of thin mineral oil; this will form a file which retards evaporation.

www.americanradiohistory.com Radio News for April, 1928 1 187 The Listener Speaks (Continued frota page !lot.) ULTWIDYPE COIVWJ7IPDER During the period of this flight, the writer was at Belle Isle Station, which is situated on a rock P t . miles long, and 3 miles wide, lying hriween Newfoundland and Labrador, ---7 entrance of Belle Isle Straits, where Pe681 NIÍpggry at the , . fllliltltl¡r-1" the Canadian Government has established a fully -equipped high -power commercial and radio direction- linding station. A THOr0-BYeéCL When Commander Byrd flew in the plane "Miss America"iica'a from New York to Paris, SuperHeierOdipre : the writer was on duty up to midnight, and The ULTRADYNE took several radio bearings on the signals A. C. COMMANDER employs the emitted by his radio apparatus (call \CT \C) most modern engineering prin- so that if, by chance, he had fallen into ciples backed by the quality the sea we could have plotted his position products bearing these trade Itirly accurately. 1'he signals of his auto - marks. Word matic transutiticr came in very loud and Vhe Last cicar until he was more than half-way across, and could even be heard until da - cLAR05TAT in Radio Reception, . light intervened. I mention this as an ex- Ç0 ample of the value of adequate radio ap- tone, greater distance, unheard O) CLEARER of selectivity - paratus on these transatlantic flights. smut these are the final achievements now available in the new Now the point is, why is radio not used Ultradyne A.C. Commander, an all -electric improved super- more extensively in planes on transatlantic ÎfiORMQN heterodyne, which has set the whole radio industry agog from flights, and also why don't these ships of coast to coast. If only for its circuit, which employs the the air earn- experienced and competent cTYIZMAN' original Ultradyne modulation system, this set would hold its own in competition, but it does is radiomen, tvla1 are well versed in the handl- itimmarlUnd more than that! It a in every sense word. ing of radio traffic, instead of men who thoroughbred of the 6§l1.nll'rdiz, Here at last is a circuit that operates on A.C.without hum. can 5 hardy receive words per minute, and It is receptive to the weakest distant signals and brings them whose knowledge of radio traffic regulations EBY J in with a volume that is almost uncanny. Coupled with the is practically nil? PARVOLT Ultradyne Power Unit it equals the tone quality of any I have heard repeated efforts of experi- receiver yet designed. enced Olen On passenger vessels Cntleavour- LYNCH Complete construction article appears in March issue of ing to work these planes, and either due to CORBETT Citizens' Radio Call Book. the inefficiency of the receiving apparatus, BIRNBACH 74 STATIONS IN ONE EVENING or the inefficiency of the operator on the Carter-, plane, extraordinary difficulty was en- The Ultradyne has an established record for distance which countered in the exchange of radio traffic. cannot be surpassed. An Ultradyne owner in La Grange, It is a well -known fact among commercial Texas, records reception from 74 stations in one evening - operators that one or both should be Stations from coast to coast and as far distant as Australia. improved. Nine thousand six hundred miles away! I would advocate the passage of a law, You can have the utmost in radio enjoyment and a real The original Ultradyne modulation thrill in the reception of distance if you assemble the Ultra- if necessary, to make these planes conform system, originated by R. E. Lacanit. is employed In this new circuit. It Is dyne A.C. Commander or have your local set builder to the radio laws of the United States, and recognized) as the rittest sensitive method Of signal reception. It will assemble it for you. carry adequate radio apparatus, and com- bring In the weakest signals and step DEALERS AND SET BUILDERS! Write for our them up to loudspeaker volume. petent radio operators, situiltn to the ocean- Distance and select pity are no longer proposition. We are exclusive distributors. Parts not going steamships. problems when the modulation sys- available from any other source. tem is employed. Rensitivlty is as- This would not only ensure the safety of sured! This new Ultradyne again proves the supremacy of the modula- life, but would be the means of saving the tion system, an original Ultradyne ULTRADYNE SALES COMPANY t'. S. Government, and other governments development. - thousands of dollars which have been spent, 509 South Federal Street, Chicago, Ill. and which will continue to be expended in fruitless search for lost planes, which can ULTRADYNE SALES CO. only be likened to "hunting a needle in a 509 South Federal Street Nance haystack." Chicago, Ill. Gentlemen: Please send me FREE 8-page Address constructional detail folder of the new 31. C. \Cusox, ULTRADYNE A. C. COMMANDER. City .Staue .. (Radio Operator') 77 Warren .l Velale. Boston, Mass. Special Library of Information NEW BOOKLET (While radio [night not ensure the safety on On Audio Amplification, A.C. of flight in planes incapable of sustaining and D.C. Power Amplifiers, themselves even temporarily in rase of a RADIO PATENTS and Specially Developed Re- foreed landing, it .would lessen the uncer- and tainty which at present exists as to the fate ceivers -How to Get Better of many «erial expeditious. In. France, TRADE MARKS Tone, Volume and Power. where commercial flight is wrure common. Newest circuits. 30 pages with radio equipment on passenger planes is re- B. diagrams and photographs quired by law.-Enrron.) JOHN BRADY Send 10e. to cover mailing cost Potent Lawyer Ouroy Building Washington, D. C. FERRANTI, Inc. Cable address: Telephone: Editor, RADIO NEWS: RADIOPAT Main 4806 130 West 42nd St. New York, N.Y. I live 150 miles north and a little west of Minneapolis and WCCO is our `local" `drive larges moths know am IN RADIO station. While listening to a national -in- heed certain simple EVERYTHING INVENTORS"'but facts before AT ATTRACTIVE PRICES. SETS OR PARTS. viol as ordered. Prompt Service. terest speech, such as the president's ad- applying for Patents. Our Munk Patent -Sense elves those Orders shipped exactly LACEY, 631 F St., Write for Prices. Mail Order Only. Send Your Address. dress, I have many tintes acts: sent. tree. Write LACEY & ALL RADIO COMPANY. 417 North rawk St.. Chiesnn turned to WOC, Washington. D. C. Established 1869

www.americanradiohistory.com 1188 Radio News for April, 1928

Davenport, or WHO, Des Moines, Iowa, 275 miles away, or WOW, Omaha, 335 miles, receiving the speech with equal clearness and volume. The larger Chicago stations, AMAZING STORIES 400 miles, are received consistently with good clarity and volume. WWJ, Detroit, 542 miles, is usually available, and WTAM, Cincinnati, 700 miles, comes in good but not regular; sonic days it cannot be heard. )forrh WJZ and WEAF, 1019 miles, and KOKA, 850 stiles, come in consistently, with good clearness and volume, any afternoon when Exciting- Original- STORIES by such there isn't an electric storm. For some Famous Writers as reason we cannot get KOA, Denver, 800 Scientific Stories. H. G. WELLS miles, with sufficient volume in the daytime; a 50,000 Each one a literary JULES VERNE though at night it [roars like wetter. The above is loud- speaker work; I haven't G. P. SERVISS treat. The plausible used the headphones on this set since test- M.J.BREUER,M.D. ing after building. It contains only seven scientific background EARL L. BELL tubes with two stages of intermediate fie - adds greatly to the can be found in the quency. My advice to Mr. Woodruff would monthly isues of be to either get a real superhet or move out remarkable interest AMAZING of the dead area. Or is Mayor Thompson these stories arouse. STORIES. causing too much disturbance with his cam- paign against the missing "haicbes:+" Seriously speaking, there must be a large absorption of radio waves in a large city 1I6 Vc'ellti 9? JulpNre-rne 9? like Chicago. I know that interference is terrible compared to out here in the large open spaces. I had my superhet in Min- neapolis where it seemed to have equal Each edition of AMAZING viewpoint. These stories reach, but a whale of a difference in noise STORIES is full of remark- make one of the most amaz- pickup. When the static season comes some of the ing collection of literary around, and this seems to be one of its able tales by works favorite spots, for pleasurable radio en- world's best -known writers. of the age. tertainment we are confined almost entirely Stories, not of this world, to daylight reception and would certainly your copy be highly disappointed if we could not reach but of worlds to come. Huge Get now. Read out. fantasies of the mind. In- these stories and feel the M. P. MASSEURE, teresting, exciting, entirely excitement which they Altkin, Minn. plausible from the scientific arouse surge up in you. (The number of letters that Mr. Wood- ruff's inquiry lias elicited is enormous, and it is evident that there is much interest in EXPERIMENTER PUBLISHING CO. daylight broadcasting. Many stations hare 230 Fifth Avenue, New York, N. Y. been authorized to use much higher power in the hours before 7 p. m., and do so; Gentlemen: this compensates to some extent for the 25c Enclosed find (check which you desire) greater dissipation of radio waves in sun- 25c. for one copy lit Incidentally, it must be per copy. 82.50 for one year subscription atmosphere. for which kindly send me Amazing Stories. remembered in all comparison of DX rec- ords that, while a good receiver has much to do with them, a favorable location is Ask Your Name also a most important factor.- Enrroa.)

Newsdealer or Address Use of Long Aerial Coupon Editor, RADIO NEWS: Mail City State With reference to Mr. Woodruff's letter, the writer recently installed a "Silver Ghost" receiver at the honte of D. G. Haley, IMPROVES TONE MUTER CLARIFIER 'l'erra Ceia, Florida, and perfect daylight The Muter Clarifier and Tone Filter, designed to pro- C. L. PARKER tect Speaker Units from the paralyzing effect of high reception was obtained from Fort Worth, "II" voltage, assures strong. full, clear tone-quality. Ex- Examiner L-. S. Patent Office Texas, and Shreveport, Louisiana, at noon. in You will be surprised at the amazing difference - reception with one on your set. Easily installed in a Attorney -at -Law and Solicitor of Patents During the broadcasting of President Cool few moments without disturbing set. See your dealer McGill Building, Washington, D. C. idge's speech from Havana, WJZ and write for full information. or Patent, Trade Mark and Copyright Law WEAF were clearly heard' at 10 and 11 in LESLIE F. MUTER COMPANY ' the morning. From 4 p. m. on, programs & Greenwood Ave., Dept. 827 -B, Chicago, III. 76th can be received from all over the United States with great loud-speaker intensity. It crrman" O. must be remembered that the temperature Skidded Grid Amplimax at Terra Ceia runs around 80 in the day- USING SHIELDPLATE TUBES TYPE SP122 Absolutely New and Different time. The fastest selling kit on the market. Ras been acclaimed Daylight reception is greatly assisted by Big New 1928 Catalog -4000 Bargains -T itest A -C "America's Greatest Receiving Set" by Radio Engineers, circuits. newest ideas In radio. at startling low islets. Designers, Editors, and Jobbers. Set BuBders have the use of an efficient antenna. At Terra The sets and parts you want. Save money. Best parts. been astounded by the revolutionary performance of this kits, complete factory-built sets. supplies. Orders fillet receiver. Write for details or ask yourldealer today. Ceia we used a 600 -foot single wire, 50 feet same clay. Write for free copy. Standard disalmis TYRMAN ELECTRIC CORPORATION high and running east and west. A sepa- to dealers. set builders. norgte. Dept. 804A, 143 West Austin Avenue Chicago. Ili. Barawik Co., 129 N. Jefferson St., Chicago. U.S.A. rate aerial is used for north -and -south re- ception. ON PARTS fine standard tube ,mindel, -"A" SPECIAL PRICES BOSCH RADIO includes five A.C. tube models, DMus shipped same day as received Tubes, Intermediate C. R. LEUTZ, matched. Dept. N. and "D" Power Units, ('one -Type Reproducers, and Phono - ,tmnstormers, condensers. etc.. peaked and graphie Pick -up device. President, C. 11. Leutz, Inc., NORTH SHORE RADIO LABORATORIES A. S. AMERICAN BOSCH MAGNETO CORP. ASSOCIATES I. R. E., A. A. Massachusetts 195 Park Place, Astoria, L. I., N. Y. 6902 North Clark Street Chicago, III. Springfield

www.americanradiohistory.com Radio News for April, 1926' 1189 A Simple Test Device Indian Program Numbers l:\V American listeners have as even WI II:N a radio set "goes dead" it is yet A New and Reproved often very difficult to determine the L. imagined that they have received the exact location of the trouble; though fre- new high -power stations at Bombay and Volume Control for quently, however, it will be found that one Calcutta, India. IIowever, the novelty - of the tubes of the set is not receiving plate seekers w'Ito are dissatisfied with the mo- "AC" Circuits current. When such t rouble is experienced notony of our own programs have a mark to Centralab Radi- a may sometimes shoot at. \Ve take a few items front :t re- small magnetic compass be I,hmsRX- 100and cent schedule THY, Bombay, which ap- used to locate the defeetive circuit. Turn of RX - 025 have the set on, place the compass in or near the pears in a late issue of the Indian Radio been built with coil or the transformer which is connected Times, with which a correspondent kindly exact taper of re- in the plate circuit of one of the tubes of the supplies us: sistance to give set, and then rename the tube from the "t'stad IIanunttm Parshad of Jaipur. effectual control socket. I f the needle of the compass moves Vocal utsic in Puni, Nat, Behag and of v o l u m e ír/ smoothly, with- when the tube is removed from the socket, K:uuotl Ragas. out blasts. " \Calw:tlkar of Ilalgantlhary Natak \Ian - jumps and sudden it indicates that a current was flowing in When the RX -100 is placed across the the circuit. The experiment should be re- dali. Dramatic songs. secondary of one of the R. F. stages it peated with each tube until the faulty cir- "Gopaldas Pctrsltnttnnulas. Vocal music surely and positively controls the tolumc cuit is discovered. It should be remem- in Bagcsluce and Yauuurkalyan Ragas and from a whisper to maximum on all signals bered, however, that in the ease of :audio a 'l'untri. -powerful locals notwithstanding. This transformers which are shielded by "B :dakrislma Bawer. Vocal music in Radiohm will also control oscillation very eITe, tively. grounded eases the compass will he unable Rageshrec, I.atat, and 'l'ilak Kantod Ragas The 11X -025 has the exact taper of re- and a ' .['unui. to detect the flow of current. It is not sistance for a volume control when placed suitable, however, for current measure - "Javaram Achrekar. Vocal music. in the antenna circuit, or across the ments; a reliable nt illi:nnnn'ter should be "God save the King-Emperor. Close primary of an R. F. transformer. used for this purpose. down " One of these two Radiohms and the Centralab Power Rheostat are essential resistanxs for all "AC" circuits. They Now Broadcasting Checks help to maintain the delicate balance of voltages throughout the circuit and in be games ',HESisS said to the oldest of no way affect the balance between plate The Community Aerial -as its partisans conveniently overlook and filament current, so necessary to the claims of dice; it is also popularly re- maximum efficiency. Gothenburg, Sweden, a new solution puted, among those less familiar with it, to for the :tp :titmcnt -house aerial problem Write for mete folder I be the slowest- moving. 'T'his may account showing applications has been found by the suspension of a metal for the fact that it has not been broadcast ring in the courtyard of a multiple dwell- CENTRAL RADIO LABORATORIES by radio until lately. The chess fans of St. ing. It is held tightly by steel wires; and 19 Keefe Avenue Milwaukee, Wis. Louis have shown some more of the spirit the radio aerials, to the number of fifty, are which made that city famous; and chess attached to it-by insulators of course -and talks are now featured weekly on Tuesday to the tops of the neighboring roofs. Each afternoons, by K\IOX of that city. We is of the 'r -type, with n lead -in from the do not understand that there is a popular center; and the assembly is said to resemble demand sufficient, as yet, to put them on the a gigantic spiderwcb. A charge of about chain programs beside bridge. fiti..00 is made for connection to this system. Incidentally, it may ho said that the Eu- ropean custom of depending upon one sta- MODERN MARY tion for entertainment, as only the local Our Dlarg's bouffit a tuperbet- 'Radio's largest- can be received consistently with crystal ill!/ 11"ORI), it is a WOW! sets, probably makes for less interference Most cotg .dation it IVIL get; hit supply house' than would he titus caused in an American 'Twill WALK them in, and Lox' ESTABLISHED If)YEARS apart went neighborhood. Poor Mary sohl her lamb and ¡ OW To KICK he with the IiOIN, We Have Complete Kits Radio Term Illustrated lint saht, "It's worth it, don't flott see, The BCLs to join." for All Circuits Her erstwhile peaceful cottage Now appearing or which have appeared in "Radio News" and other publications Is now the scene of WARS; The family for the locals 1VAIT, Set Builders While Mary will WOO Mars. It will pay you to send for our Pother says, "Now EUT it out!" Circuit Booklet and Catalog He's a. perfect 1VREC, you know: For 1VATT little sleep lier poor Dad gets Our Excellent Facilities and a Trained Is 1VIIN the batteries are 2LO. Technical Staff are always ready to give you the same service that has satisfied W. Sixte. -Joseph thousands since Radio became popular.

RIGHTEOUS RETRIBUTION M. & H. Sporting Goods Co. 'I'he Queen of hearts, She made some tarts 512 Market Street Philadelphia, Pa. Prone a radio recipe; The Knave of hearts, He stole those tarts And suffered perceptibly. ; .1 fsa KeYourRadiow.SAY,', -Popular Radio Weekly, Australia. Wdny. (Original source not given.) dnytuingYoU THE SKY IS LIMIT Brand Idea fera a Partyiet 401044,111' The Mystic luaus Broadcaster Gk.m THE SPRATTS itaminuteto ioomo.Noet. r,. nut.rinto(h Tre,,the,ats -_ star tex Brrohbaate TMm, the fun .... Jack Sprat( liked Mike and Pat, Te,mita. tha nxtno Sena poney. Try ilmtma aortic5 Oontaparty. Sana no money. His wife liked String Quartets: Irae óa1.95$4.95 alum, ulagm for MM1n ey I ear a. n :,Marp - mener And so betwixt them both, you see, bath É Lea Faa DUCTS 01. Deal 224 "INTERFERENCE" They had two radio sets. ï26 Atlantic Ave.,a B'klyn, N.Y., -The Listener -In, Melbourne. P. P. A., in New York World. BeYour Own Broadcaster

www.americanradiohistory.com 1190 Radio News for April, 1928

OPPORTUNITY AD -LETS Follow these advertisements every month. Reliable advertisers from all over the country offer their most attractive specials in these columns. Classified advertising rate twenty -two cents a word for each insertion. Ten per cent discount for 6 issues, 20 per cent discount for 12 issues. Names and addresses must be included at the above rate. Cash should accompany all classified advertisements unless placed by an accredited advertising agency. No advertisements for less than 10 words accepted. Objectionable or misleading advertisements not accepted. A dvertisements for the June issue must reach us not later than April 1st. CIRCULATION LARGER THAN THAT OF ANY OTHER RADIO PUBLICATION EXPERIMENTER PUBLISHING CO., INC., 230 Fifth Avenue, New York, N. Y.

Agents Wanted Help Wanted, Instructions Patents

Earn $25 Newspapers fast sales. Every owner buys gold Weekly Spare Time. writing for Inventions Commercialized. Pat cut ed or Big Money and and Magazines. Experience Copyright (took. noontide& initials for his auto. You charge $1.30; malte $1.35. Ten Unnecessary. Write Adam Fisher Al fg. Co.. 227S Enright St. Louis. bio. for leu lars and free samples. "_Hmv to write for Pay" Free. Press Reporting Inst., orders daily easy. Write part 073. St. Louis, blo. American Monogram Co., Dept. 133, East Orange, N. J. l'rrntìn liu racin rund .11altigrnphing Do you drive a Chauffeur- Guaranteed Genuine Gold Leaf Letters anyone can put en car? U. S. Government Free Carrier job pays $141 -$175 month. "Itavr to Qualify" store windows. Large mats. enormous demand. 200 Letterheads and 100 Clark, Chicago. mailed FREE. Write, Instruction Bureau, 251 Arcade Envelopes, $1.10, postpaid. samples. Met allie better Co., 422 N. ilidg., St. Louis, bio. 01hE11bl.AN COMPANY, Box 1208. Chicago. Sell subscriptions to magazines known the world over. .... nm, nn ,n,n, .n,n,mn,nnnnn.n,n,nn.on,nn,nnn...... M ulti graphing, two dollars thousand. Miscellaneous Steady monthly income with absolutely no investment To- Priming, Mayer Rev Corporation. hlonuwuth, Illinois. nulred. Hundreds of selling arguments every month. Start Instruction now. Full information sent free. no obligation. Agency Publishing Co., 230 Fifth Avenue. Division, Experimenter Learn Sloane, New York. Chemistry at Home. Dr. T. O'Conor noted educator and scientific authority. Will teach you. Printing Outfits and Supplies Our home study correspondence course fits you to take a in business and help you ac- Agents -We start you as chemist. OR page 1095 or experience needed. Snare or full tile. position See our full-page ad Print your own ed. No relit al 01 this Issue. Chemical Institute of New York. 1d E. 30th cards. stationery, irculars, paper. ere. . -$1 Madison Products. You can earn -n oti weekly. Write Street, New York Cits. Complete outfits $8.85; .lob Presses $11. $29; Rotary 5149. 520 Mom bray. New York. Print for others, big profit. All easy, rules sent. Write for rat alog presses, type, etc. ICeisey money. paper, Company, Big bunch Mail. Year 17.c. Cotalogoes, :naeazines. Learn Photography at home. Make big Quick. F -13, bleriden, Conn. Kentucky Agency. Covington. Kentucky. new system. New Ore booklet: "Simplified hPhotographr " Ajax Studio & Labor:ucries. 511N Columbus Circle, New York. Our Superior Proposition will net you SI00 e week. every week in the year. Enuipment and car furnished. No capital tar experience necessary. Immediate profits. Write Radio Imlay for particulars. .AMERICAN PRODUCTS COM- i, Miscellaneous PANY. 1503 Monmouth, l'inctnn:u Ohlo. Press and publie concede it to be the best ever tarodvrel. Radio Theory and Opera! ing.' by Mary 'l'exanna Loomis, Inventions Commercialized. Patented Cr Vnpatented. member lost hut e of Radio Engineers, Lecturer on radio. Write .dam fisher 31íg. Co., 278 Enright, St. Louis. Mo. Loomis Radio College. Thorough test nd reference hook; Business Opportunities Sur pages, 700 illustrations. Price $3.50. postage paid. Save Money at Home. You can build many home neces- Used by Itadlo Schools. Technical Colleges. Unit ersities. Dent. of Commerce. sities yourself, such as I ornit ure. kitchen utensils. decora- Gov't Schools and Engineers. At btokdealen. or sent on receipt or order. Inventions Commercialized. Patented or Cnpatented. tive mat erinl. etc., thus saving many dollars. ,All onstruc- check mono) ' Loomis Publishing Company. fuite dam Fisher Mfg. Co.. 278 Enright St.. St. tional information on hundreds of things in 116 -page Dent. It. 405 -901 St.. Wash- given ington. D. C. Louis. Mo. book "How to Make 1t." Price 50e. Experimenter Pub- lishing Co., Inc.. 230 Avenue. New York. Fifth 100 67 Ways to Increase Income. 96 -Isaac look "Spare - -volt Edison element recharge:d, he "it" halt cry kit $8.00. 140 -volt. $11.00 180 -volt. tlnte Money Handbook" contains 97 practical and complete Send us your portrait and we will enlarge it for $5 00. $1.1.00. "1:" Charger 82.00. Edison elements with melded connect ors 5c pair. plans to tuterate sparet lune business. For everyone who Ben Griop, Carthage, Mo. Seul for more money. Price only 50e. Consrnd Company list. Zied. 634 North Randolph. I'Iti ladelnhi n, Pn. hoca., 230 Fifth Avenue. Nen York. h. Send Transformer forms turned from wood, 25e ea, Transformers 9950 -7n_, 50 -7;, $4.110. sketch. Mabry Itadlo Shop, Beaumont, Texas. 1912 Hanel. $550. Knock- with down primary only 5:1.00. Write for lists. Radio l'uns Amateur Cartoonists: Make money in spare time Sales Co.. Orange. N. J. new cartoon selling plan. Write Smith's Service. Wen- Forms to Cast Lead Soldiers. Indians, Marines. Trap atchee, Wash. pers. 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Old Coins Wanted: Mien to work wit h National Radio Service Or- ganization. No selling scheme. Co- operatic Radio Doc- Chemistry Dept. Old Coins. Large Spring selling catalogue of coins for tor, N, 131 Es°oi St., Salem, Mass. sale. free. Catalogue °noting 10e. Home. Dr. T. O'Conor Sloane, prices paid for rotos. Learn Chemistry at \\'111iam Hesslein. 101 K. Tremont St., Boston. Mass. ,:,o.nnnnunn,,:o,m,mn. nnted educator and scientific authority. will teach you. Our .nnne,n,,,,mm..unn.,nnnmm,n..n,onam', home study correspondence course ills you to take a position as chemist. See our full-page ad On page 1095 of this Salesmen Wanted issue. I 'bemire! Institute of New York, Dì E. 30th Old Money Wanted Street, New York City. A paying position open to representative of character. Take orders shoes. hosiery. direct to wearer. ..,n,n,nn,n"'" n n,,.,,, $2 to $500 each paid for hundreds of Old or Odd Coins. Gond income. Kern all old money. it may he very valuable. Send IO for rnnnanent. Write noir for free honk. "Getting Ahead" Tanners Shoe 11íg. CO.. $74 So. C. St.. Boston, Maass. Correspondence " Courses New Illustrated Coin Value hook. 4x0. Guaranteed priers. Get posted. We pay Cash. Clarke Coln Company. 14 Street, LeRoy, N. Y. Used correspondence school courses sold on repurchase basis Also rent ed and exchanged. ?foney -hack guarantee. Old 9100.00 Scenery to ). Mountain, Pisgah, Rent Caning tree. (Courses bought Lee : 55n.Wanted.fo 19131 Libériy ed Nickel14(notDBuf- Alabama. falo). Big premiums paid for all rare coins. Send 4e for Largo Coin Folder. May mean much profit to you. World's M ost Beautiful settings for operas, plays, Min- ,,,,.,,,,,,,,1,,,.,,:,.n:..,,,,,,,,,,,,,,,,,,, 1,,,,,.,,,,,.,.,,,..n.1 ..... 1,,,na,,,,.,,. 1n11n111n1n1n1nnm Numismatic Co., Dept. 112, Ft. Worth, Tex. strels. .Amelia Grail, Philadelphia, Detectives Patent Attorneys Detectives Needed Everywhere. Travel, Esperienee un- Song Writers necessary. Part 'colors free Write, :American Detective System, 2190 Broadway, N. T. Patents-Send for fora, "Evidence of Conception" to be signed and witnessed. Form, fee schedule. information free. Sena Writers-Substantial Advance Royals les are pa Id .,,,,,,,n,:,,,,:,,,,..,,,., Lancaster and Allwine. Registered Patent Attorney's in on publishable work. Anyone having original ideas for ...... ,,,,,,.nn,n,,.,,,, United States and Canada. 269 Ouray l lids., Washington. figs may submit poems for examination and free advice. Electricity D. C. Walt or Newcomer, 1074 Broadway. New York. Patents-Send drawing or model of your invention for ..... , .w n,,,,,,,, ...... Electric Fun ! Seventy stunts, 110 volts, $1. Cooperco, examinnt Ion and instructions. Advice and booklet free. Campbell. Calif. Highest references. Best results. Promptness assured. Watson E. Coleman, Patent Lawyer, 724 0th Street, N.W., Washington, D. C. Telegraphy Inventors- Should write for our Guide Book. "How to -Both Morse and Wireless taught thoroughly. For Inventors Rig salaries. Wonderful opportunities. Expenses lose. Obtain a Patent" and Record of Invention Blank. sent chance to earn free. Send or sketch of inventions for our Inspec- part. School established fifty years. Cata- model log free. Dodge's Institute, Cour St., Valparaiso, Inventions Commercialized. Patented or Unpatonted. tion and Instructions Free. Radio, Electrical. Chemical. Ind. Write Adam Fisher Mfg. Co., 278 Enright, St. Louis. Mo. Mechanical and Trademark Experts. Terms Reasonable. Victor J. Evans R- Co.. 922 Ninth. Washington, D. C. ,:::, :,,:,n:nnnonnn:,n,,,,,,,nn, .o,n.,n,.:...... n,n.nnon,onm Potent Sense- Vcluable book free. See Estoy's ad. page Wanted to Buy Help Wanted noi. Lacey & Lacey. 631 F. St., Washington. D. C. Established 1899. Full Value Paid for Old Gold Jewelry, Watches, Dia- National Publisher. needs scents. boys and shops to Wanted. Ideas. Demand for novel devices. however small. monds. ermine, bridges, dental gold. silver, platinum. gold help sell great national magazines. No investment re- If patentable. may be the means of your independence. or silver ore: magneto points, old false teeth. Packages re- Wtired, Big profits, sparet hoe work very essful. Patents obtained. Sales negotiated. Advice free. IN- turned if nur offer is not safisfattory. T'nited States rite Agency Division. Experimenter rim. Co.. 230 Fifth VENTORS SERVICE, R17tEA1-. Box 1045. Washington. Smelting Works (The Old Reliable). 39 So. State St.. Avenue, New York. D. C. Dept. 10. Chicago. III.

www.americanradiohistory.com Radio News for April, 1928 1191

12:30 to 1:30, very clear and distinct, no failing- Set Constructors' Letters just a little "steaming" one gets occasionally when from 1147) tuned to a distant station. There is great interest (Continued pale being taken in it locally; but it gave me a thrill FERBEND when it performed so faithfully at first. and help. Please be so good as to publish this, I use two aerials: one in the basement of 35 as 1 am almost inundated. feet, and an outside one of 120 feet (too long). Of all these letters which I have received, only The inside one gives me as far as Kansas City or a comparatively small number enclosed a stamp EALKAGAIN Lincoln, Neb., etc. Rut the reproduction! It is for reply. Those who did not I have not an- simply wonderful. LEONARD F. SCOTT, steered; as had to draw the line somewhere. I 670 Jane Street. Toronto, Canada, I SID not a Member of Parliament or a Congress- man, consequently I can not send my correspondence "franked." Let me say to those asked for information and plants that they will find complete information in I Want To Know RADIO Nrws for October, 1927, or Rubio NEws (('rail( inueil from purge 1152) I llueprint No. 31. I have done considerable ex- perimenting with the hook -up and made certain changes which, in my opinion, are improvements. There is still another type of electrolytic recti- if any of your readers desire this information it fier which is very efficient. 'Phis consists of a may be obtained if they will send a dime for same; tantalum plate and a lead plate in a solution of .sulphuric no attention will he paid to letters otherwise. acid and distilled water; this solution Many correspondents report great difficulty with should have approximately the sante specific gravity distortion. Let me say that I have the sante as that used in storage batteries. The advantage of is trouble here; while a friend using a Short-Wave this type of rectifier that the tantalum does not as receiver about a mile front me gets the Short -Wave corrode quickly as the aluminum, and natu- broadcasts with perfect clarity. The answer is, rally the electrodes last longer. Another advantage evidently, location. 'There is no remedy known is that this type of electrolytic rectifier does not NOW!- Lowest -Priced ^ heat up as quickly as the other. except to move: Quality Tube " B " eltP (a,[ l might mention that 5S \V at Chelmsford, Eng- 7 Eliminator - - - - 050 land is now on a regular schedule from to K a.m., and 2 to 5 p.m., E. S. T., daily except .1.V Since 1921 Ferbend Products have .. Saturday and Sunday. The broadcast is by remote :ICKA'OIFLEDG3JE.CT been famous for outstanding Complete, control from 21.0 at London; announcements are 77We data which form the answer to ques- quulitl' and long -life efficiency at lowest prices -prices "Within Including eery infrequent. The wavelength is 24 meters. tion number 2265, printed in the "I Want Reach of All." Long Life Perfected (Atti. W. UEEsv, 7n A:nme" department of RADIO NEWS for The new HEAVY DUTY "B" 85 MIL. TUBE 146 Market Street. Hamilton, Ontario, Canada. February. 192$, were taken front the Radio Power Unit is no exception. In I broadcast Laboratory Information Sheets workmanship, performance. ma- terials and appearance it Is the Delivers np to ISO (Mr. Reese', offer is so plainly not intended (Nos. 27, 28 and 65), and should have been equal of any. we INVITE volts on any set for profit, that it is given here: though this de- credited to that .ounce. Acknowledgment comparison. partment is obviously not a mcdiut on for the sale is mar herewith to Radio Broadcast Maga- SEE YOUR DEALER, OR NO LIQUIDS of information and diagrams. The good nahnv zine for the voluble information. SEND DIRECr of an experimenter who is milling to impart its Shipment will be made upon re- OR ACIDS O. D. Use for formation as to his results should not be imposed ceipt of price or O. thirty days to convince yourself - 1! peon by the merle- cuilotas. and correspondents t hen If not satisfied write us with- should bear in mind that they may number in that time and purchase price 10 Days' lair will he refunded. Order today'. .} Trial ¿reds. Incidentally tee may say that the October, Radio News Laboratories 1927, issue of RADio Nsws has been exhausted, proving the interest of our readers in short -nave (Ninth, Heil front page I11.9) reeepliou. For that rea.to,, an excellent unedel, FERBEND ELECTRIC COMPANY which should prove equally serviceable, is described 425 %VEST SUPERIOR STREET CHICAGO, 11.1.. at length in this issue of RAOt) NEtes. Ire shall be glad to hear of the results obtained.- Entree.) YAxLE Na440 all Automatic ` AN UMBRELLA AERIAL \ \1 Voltaree ltclay Editor, Rnuto NEws: I ¡un enclosing a picture of my residence, show- ing a type of aerial which cats lu installed con- veniently where there is no room to string a long wire. I have copied very good distance; received KFI on this aerial. It contains over two hundred feet of wire. (Sec page 1147 for picture.) I IARwLI, IL I i ukt.r.Y, nn,r 355, Lake Cost, .Vest' Jersey. (Under conditions such as those described, it is possible a of to put np system this kind, with AWARUf:u Tlll'. I'.\ )TO \E\VS LABORA- considerable signal -collecting rapacity. in n small area. 71e length gins,, however, is rather too TORIES C'EIC'l'IFIC':\'l'E OF \ ERIT NO. 2290. For automatically switching on and off your much for selectivity uilh an ordinary receiver. 13 Eliminator and Charger, or either, and in -Entree.) addition, automatically switching off your Charger when the battery is fully charged. MULTIPLE SPEAKER SWITCH THAT SIBERIAN TRANSMITTER With the Full Automatic Voltage Relay 'l'he demonstrating unit shown is a very practical Editor, RADIO NEws: it is now practical to utilize the advantages I of switching device which allows comparison of various have heard the announcer the Siberian short- of a high rate charger and at the same wave station at Khabarovsk giving call of RSN loud speakers and phones. It consists of a small time control the switching of the charger and his wavelength in English last night. Ile neat wooden box, 41/ x 3Æ4s x inches, carrying a as well as Eliminator with the switch gave it as. 56 meters. This conies in on my set, small hakelite panel 4% x 3% inches. On this panel the B a -' :hich is fully shielded, at about 44 on the dials are inottnted switch and five contact points, and or filament control on the set. with a 12 -turn coil; and Kl)K:\ at 54. I have in it are drilled six pairs of holes to fit standard heard C2N11 and PCJJ and one Japanese; others phone tips. Five pairs of tips arc for the instrte No. 440 $7.50 too weak. metals to be tested, and one for the output leads C. A. BLAciINGTOx. Yaxley Mfg. Co. I I 'rm,pell, Alaska. Dept. N, 9 So. Clinton Street (:l Japanese friend, 31r. N. Miyake, favors its Chicago, 111. with a pees dispatch indicating that "'RF3I,' operating on 60.12 meters. has berm heard quite distinctly in Japan every night from about 7 to 9 p. ut." This is from 5 to 7 n. m., 17. S. Eastern Standard Tinte. It is quite possible That this 20- kilowatt phone station has been roving[ the short- 'Van` band.-Eon TOR.) Big New 1928 Catalog - Shows latest A-C circuits. nearest Ideas. 4000 leaders. Cet sets and parts you tuant here. Sate money. l'arts, kits, MORE WORK ON THE PERIDYNE from the receiver. Inside the box, ten springs complete factory-built sets, supplies. which make contact with Editor, RADIO NEws: the phone tips are ar- Quick service. Write for free copy. - s ranged in two rows; those in the first are elec. S :anrferddtsmm,e to dealers. .cri 'Whirrs, lit answer to your request for letters from aaents. Barawik Co.. 129 N. Jeffer- trically connected together and to the correspond- son builders of the Peridyne, here is ' , with very St., Dept. 804, Chicago, USA. ing contact springs of the incoming The many thanks for the guidance in setting it up, as lead. other five springs are well as the good results. I had great faith in its connected, each to a contact point. and the second input lead spring possibilities of reception and performance, the first through its contact is connected to the switch. The operation of this time T saw the hook -up, but it has really passed my switch is very satisfactory. expectations. MERSHON CONDENSERS The first night, KFI and other distant stations AWARDED TTTE RADIO NEWS T.:\T1OR: \- For fu li Imnrmat to a address Department RN. galore. was listening to THE AMRAO CORPORATION I XVI this morning front TORIES CERTIFICATE OF MERIT NO. 2291. Medford Hit side Massachusetts

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The MOST Sensational "B" Eliminator Announcement ever Made! NOW-you can buy as good a as is possible to build - at a price that won't cramp your purse. Now -you can enjoy the thrill of buder, clearer, better reception that a good "B" Eliminator affords. And you buy the PEERLESS withoat risk of any kind, for it is backed with a 2 Year Guarantee This astounding rifer is without a precedent. Never before has such a -+slue been offered. A "180" volt "B " -a 'B" that will r-m your set and a power tube too Uses The PEER -and guaranteed for two long years -at the ridiculously LESS Is small, low price of only $12.45. thin and compact. 85 MIL.TUBE Slides Into small spaces, table type cebl- nety. etc. Case Is heavy steel. maroon crackle finish. Delivers Comes complete With cord and separable plug. 30 DAY TRIAL Read all about this great new, better, tube type "B" Eliminator in the left column of this page. Then order it at once. Hook the PEERLESS up to your set. Compare the reception you get to that which you got before, or to that 180 VOL which you can get from any other "B" Eliminator. Put the PEERLESS to every test you can. Make it drive a "171" power tube, if that's the tube you Because of its very low price, don't confuse the PEERLESS with use in your set. Enjoy this "B" for 30 days. Then-send it back. if you think Eliminators which deliver only 90 or 100 volts. Also, don't confuse that any other "B " -at any price is as good. We'll refund your money instantly. it with chemical type Eliminators. The PEERLESS uses the standard 85 milliampere gas -filled Raytheon or Q. R. S. rectifying tube. It is dry. No water, no acids to add. Requires no attention whatever. Mail Coupon Delivers pure, hum -free "B" current of 221/2 -45- 90-135 and 180 volts. Out -put Voltage taps are fixed. No adjustments. Will run any set. Will operate any power tube requiring no more than 180 TODAY volts. Will not "motor- boat " on superheterodyne receivers. Operates Send only $1. A dollar bill will do. We'll ship the PEER- resistance- coupled audio amplifiers, when other "B" Eliminators LESS "B" Eliminator at once. Pay the expressman $11.45 fail. In every sense of the word, the PEERLESS provides the finest plus small express charges. Remember -you order e k ind of "B" Eliminator performance -at only $12.45. Why pay more? the PEERLEaa entirely at our risk. It is yours # to test foror days.a s. YouYou et yourour mone # back promptly if within that time, for 1 any reason whatever, you don't want to keep the PEERLESS. Order .0s now. Fill in the coupon and ¢y ey4 mailmaI today. ,..11/ 4$ 9 TUBE PEERLESS MFG. CO. FREE 494t°e 3977 Cottage G rove C1a, 1 SPECIAL INTRODUCTORY OFFER Avenuesue , gP t Chicago, Ill. This is first of this -powered, , .°. CrP ad 9g the announcement new, super better quality guaranteed "B" Eliminator. Its regular price is $12.45 with- Cc's` 41P °t e out the rectifying tube. But, as a special introductory offer to get v t' thousands of these units out on sets, we will include, for a limited , ' time only,a genuine $4.50 Q. R. S. 85 Mil. Tube free with your or- p 5 , . t der. Think of it! A 180 Volt "B " 2 year guarantee -the privilege -a \esgG° c of trying it 30 days at our risk-and a $4.50 tube free -all for $12.45. SQ° c t't.0$0e Mail coupon now. 99ry1 1

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FOR THIS ttEGULAR$IZ A: C Fil TItANSFORMER t Now-at a reasonable cost -you can build a set using set into an A -C set. LOOP Supplies Proper A -C tubes, or convert your present for T is new, advanced type, better quality, heavy duty SWITCH oltages for All 226, 22 supply transformer is now available to The loop of wire .1lament shown ilacic of the and 171 Tubes '''"_at the very low price of only $4.87 - instead tranef . e is an d ; he $12.00 price at which it has always sold. extensfol( ... üde of this A -C Filament Supply Tra the 110 It19 p With You can't buy the equal of this transformer any vided ` venien former yot. can operate a set combining uf t rh to cu n $12.00 or $14.00. Why pay 2 tubes pla,;d': . ,+ ch to type 226 A -C tubes, type 227 and more waken this unit is fully 2 type 171 power tubes. Hence, the most ?`',, borate super-heterodyne receiver may rated with this unit. Each of the th secondaries are center tapped, thereby doing ANTEED away with 'the-. eed for center -tap resistances Guaranteed to deliver the correct voltages at the required by oth of filament transform taps as ragrked- Guaranteed against def et in mate- Don't confuse the is A -C Filament Trans - rial and workmanship- Guaranteed the best per - tonner with others which supply.only tiv, `orming A =C filament supply transformer built. and six tube sets. orks Perfeei«m With the TRY IT FREE New A -C eases Test This Unit at Our Risk Use the Illinois A -C FIIa_ment Order it. Connect up to your set. Check the voltages with an Transformer with the new A -C accurate voltmeter, if you like. Put it to any test you wish. c-onversiorc harm . ' onvert any If you think, for any reason at all, that this unit is not the attery ope1..2144A to an A -C best A -C filament transformer you can buy, send it back et in a few mien time. Enjoy and your money will be refunded to you instantly. You e freedom from "A" battery are the sole judge. Order NOW. Attach dollar bill to uisarn-e which these new har- the coupon and mail Tight now. Pay postman $3.87 n44:11ti and the Illinois plus few cents postage when the transformer arrives. Remember take no risk. A -C Filament Transformer Then, make your tests. -you maces possible. Order Guarantee protects you. Clip coupon. Order today. one of these guar- me ow The units to- Famous day. Take ad van- ILLINOIS "All -Frequency" age of the low MAIL THIS COUPON i ILLINOIS TRANSFORMER CO., Dept. 101 I AUDIO TRANSFORMERS $4.87 Price. 223 W. Elm St.. Chicago, Ill. LIMITED I enclose $1.00. Please ship me one Illinois A -C Filament Trans- 1 former for 226, 227 and 171 standard tubes. I agree to pay ' OFFER 97c Each postman $3.87 balance and small postage. It is understood that I can have my money back if not satisfied. This is the most amazing ' radio value ever offered. Think of it! A $4.00 audio p, I enclose $ Ship me the following Illinois Audio Fre- transformer -a real "all frequency" unit of the finest musical capability, offered quency Transformers: I , . I ; direct from the factory for only to I; 1 to I 97c. Never before such a bargain opportunity. 5 to 1. I understand I can have my money back if Thousands have bought them. Sold with a positive guarantee of satisfaction or not satisfied. ' money back. in Supplied ratios of 1' tot, 3to1and5to1.Ordernow.Usecoupon. Name t ILLINOIS TRANSFORMER CO. Street Town Slutr 223 W. Elm St. Dept. 101 Chicago, Ill. rres.OM am *ma

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